The Components of Going Faster [Archive]

Larry Gibson

04-01-2022, 09:40 AM

I posted this some time back in response to a similar question. It may help, along with the responses above, to get you started.

HV cast bullet loading

Numerous others and I have worked bullets such as 311291, 311041 and several other cast bullets of the bore riding nose design every which way at higher velocity. Normally best accuracy comes in the 1700 – 1900 fps range as reported. That is within the RPM threshold for the 10” twist. You may or may not believe there is an RPM threshold but it’s what’s giving you larger groups as you increase the velocity and RPM above 1950 fps. Working different alloys, powders, sizing, GCs and lubes I was able to maintain 2 – 3 moa at 2200 – 2300 fps with the 311291 for consistent 10 shot groups at 100 yards. If you want to improve on that accuracy at or perhaps a little higher velocity I suggest you change bullet designs and pay particular attention to minute details when casting and loading.

Bullet; with the ’06 the ideal cast bullet design is one that has minimal lube groove depth with enough lube for the length of barrel. It should have a short nose with minimal ogive of not more than caliber length. The bullet should have a bearing length from the beginning of the ogive to the base of the GC. That bearing length should just fit within from the base of the cartridge neck to the beginning of the leade. Two designs fill those requirements in most ’06 chambers; the Lyman Lovern design 311466 and the LBT 150 gr. With either bullet design moa accuracy with 3 -5 shots is obtained with proper casting, sizing and loading in the 2200 – 2300 fps range if the rifle/shooter are capable with a 10” twist rifle. With either cast bullet such accuracy (1 – 1.5 moa w/10 shot groups) can be obtained at 2400 – 2500 fps with a 12” twist and 2600 - 2700+ fps is possible with a 14” twist.

[Note as of August 6, 2020; Since this was written we have learned a lot more about shooting naked and lubed cast bullets at HV, but the basics are here. There are also a few newer bullet designs available especially for HV shooting. I highly recommend the NOE 310-165-FN “30 XCB”. It has proven to be an excellent HV bullet but does extremely well at “normal” cast bullet velocities. PC’d and PP’d bullets add another dimension.]

Alloy; I’ve found a strong yet malleable alloy of 18 – 22 BHN to work best. A hard brittle alloy with a high antimony content should be avoided. Lyman #2 alloy WQ’d out of the mould works very well up through 3000 fps.

Cast bullets; they should be visually inspected under a magnifying glass for any defects. If using a multiple cavity mould they should be weight sorted if they do not weigh the same from each cavity. Weight sorting is most often done incorrectly for what is needed for HV cast bullet shooting. A search should find my posts on how weight sorting should be done.

Gas Checks; bullet bases must be square and flat. If the sprue cut of is not even with the bullet base cut a sharp knife can cut it flat. GCs need to be soft so annealing them may be necessary if they are commercial. I use my own made from .015 brass shim stock. The GC should be a tight slip fit on the bullet shank. It should not be forced on and swage the flat bottom of the shank. [note; I have found the slip on GCs do not stay on with many HV loads and are detrimental to accuracy when they come off.] Thus I exclusively use Hornady crimp on GCs now. Even they can come off above 3000 fps but that’s outside the realm of this discussion. A GC seater (I use the Lyman on a 450 with a .311 H die) should be used to squarely seat the GC and crimped on in a separate step before sizing/lubing. I then lube in an H&I die of the same size as the “as cast” bullets. The GC’d and lubed bullets are then push sized the bullets through a Lee .310 or .311 sizer after.

Bullet lubes; I’ve run multiple tests at HV with various commercial lubes. I consistently get the best accuracy with Javelina lube followed by 2500+. At high velocity/RPM the bullet lube needs to spin off very quickly and completely. Hard lubes do not and small chunks of lube sticking to one side of a cast bullet will unbalance it with inaccuracy being the result. Softer lubes work best at HV and I’ve yet to find one that betters Javelina.

Cases; should be “match prepped”, well fire formed, neck sized with .002 neck tension, with uniform neck thickness.

Powders; I’ve had best results with AA4350, RL19 and H4831SC. If loading density is below 80% I use a dacron filler.

Primers; I’ve also ran numerous tests with different primers. “Soft” primers will lower velocity and RPM with these slower burning powders. Accuracy will appear to be better but it is the lower velocity/RPM from such. Load all to the same velocity/RPM and it’s hard to pick a “best” primer. I mostly use WLRs because that’s what I buy in bulk. Magnum level primers are not needed in the .308W or ’06 with these powders and give higher SD/ESs which isn’t good for accuracy.

There you have my advise based on “been there, done that” numerous times. My best advise if you want jacketed bullet accuracy at jacketed bullet velocity in a .308W or ’06 is to get a quality 14” twist barrel 26”+ long and follow the advice I’ve given. You will be amazed at how easy accuracy at HV then comes with cast bullets, even with 311291 and 311041.

Or, if you’re really interested you can build a HV cast bullet rifle. Here’s 11 shots (supposed to be 10 shot group but I lost track of the number of shots) in 5.9” at 600 yards from my 30x60 XCB shooting the 30 XCB cast bullet at 2900+ fps.

298410

Forrest r

04-02-2022, 07:51 AM

Myself, I haven't done a lot with hv cast bullets but I did put a bbl on a old canadian shooting team cil 950t. It's a puma rifle made by savage & I ended up putting a shilen replacement barrel on it. The receiver is the small shank along with the older style with the 4 3/4" hold down screw spacing. I wanted a long bbl but the tradeoff was it had to be lighter due to the smaller hold down screw spacing. The original bbl was 25" and had a puma contour (it was a canadian shooting team puma rifle). I ordered a 30" bbl with a standard puma contour, a .336 1.5* match chamber (308w) & a 1 in 14 twist.

I actually wanted the bbl to use with the jacketed 155gr smk bullets. But it makes life interesting with cast bullets. Everything is a trade-off.

The 308w cartridge isn't the best choice for case bullets with it's short neck. A lot of cast bullets have to seat deep to fit the throating which puts the base of the bullet in the boiler room. The long bbl does have a "whip" to it and does show vertical string when heating up from shooting with too fast of a cadence. But I do get a lot of velocity out of that 30" bbl and the 1 in 14 is a slow enough twist to play around with cast bullets doing up to 2700fps.

Some interesting things I found with my very limited testing.
The bullets nose makes a huge difference. These bullets were cast from a 2-cavity cramer mold with 1 cavity having the hp pin. This makes from an extremely strong nose on the cast bullet.
https://i.imgur.com/yl6sLkT.jpg?1

Didn't matter what load/powder combo I tested, when pushed over 2200fps the sp bullet's groups always opened up compared to the flat nosed hp bullets. Typical groups
https://i.imgur.com/uLdIPcZ.jpg

Lube plays a huge roll in accuracy of hv cast bullets. The 1st testing I did with that new shilen bbl. I wanted to see if I could hold 10-shot groups to 2" @ 100yds and have the velocities in the +/- 2600fps range. Not really lofty goals for some casts but it was asking a lot out of me. Anyway I cast up a bunch off lee 160gr tl bullets and did head to head testing with traditional lube VS pc'd bullets. The traditonally lubed/sized bullets.
https://i.imgur.com/y5CttId.jpg?1
The pc'd bullets.
https://i.imgur.com/tEeK5wb.jpg?1

The pc'd bullets got higher velocities, I can only assume it's from the pc process itself. The heating of the bullet backing on the pc will actually soften/anneal the cast bullet. This makes the softer bullet expand/obturate/seal faster/better with the pressures of the loads being used making them more efficient.

The other thing I got out of that initial testing was the 37gr load blew out with the traditional lube. I took the same lubed bullets and added 45/45/10 tumble lube to them and re-tested. Turns out I didn't have enough lube with the 1st test & it's was actually interesting to see that while I didn't have any leading. Accuracy went south when there's not enough lube.
https://i.imgur.com/QCvbTnt.jpg?3

When I started pushing the pc'd bullets over 2700fps I started seeing this in that shilen bbl.
https://i.imgur.com/ltVgHNy.jpg?2

Bore-tech eliminator took it right out. Others have said some pc colors do this while others don't. I'm using smoke's john deere green & again I simply gave the pc'd bullets a coat of 45/45/10 tumble lube and the black burn marks/streaking went away.

I ran into an interesting issue with the xcb bullet. The lee bullet I use is similar in design to the xcb bullet. I did an initial test with the xcb bullet using 36gr and 37gr of h335. The results were terrible, had shotgun patterns on the targets. 2 years later I got the time to take a look at what was going on with that xcb bullet. So I re-tested and this time I decided to use 2 different gas checks. It just didn't make any since that the lee bullet would group and the xcb wouldn't. Same alloy/sizer/lube/ETC. In all my testing so far I used my home made al gas checks. This time I used my home made al gc's VS the store bought hornady copper gc's. Sure enough at lower velocities it didn't matter. Pump up the volume (velocity) with my home made al gc's on those xcb bullets and this is what I ended up with.
https://i.imgur.com/38RjGuP.jpg

Well there's 4 things I found with my limited testing/playing around with hv loads and cast bullets:
The shape of the bullets nose plays a huge role in accuracy when pushed hard.
The lube or more precisely the lack of lube will ruin your groups.
Driving pc'd bullets over 2700fps (140,000rpms) caused the pc coating to leave burn marks in the bbl that a simple coating of tumble lube took care of.
The difference in the material the gc's are made out of along with how hard/soft (annealed) they are affects accuracy when the bullets are pushed hard.

If I were to buy a barrel strictly to use as a hv/cast bullet shooter I would buy another shilen bbl with the same .336/308w match chamber. But this 1 I would send my 1* throating reamer to them and have them cut the chamber and put a 1* leade in the throat. This would allow the bullets to be seated out further. The new bbl would be a 28" bull bbl with a 1 in 16 twist.

dverna

04-02-2022, 09:05 AM

Forrest r,

I enjoy your posts and this one is an example of why. I look for honesty/reality and not a couple of "wallet" groups...or the thing that is a sure sign of BS..."When I do my part".

One question...what was the traditional lube you used? Larry made a comment on his post about getting his best results with Javelina (as it sheds easily) and he had good success with 2500+.

Again, good post!!!

Hanzy4200

04-02-2022, 12:05 PM

I'm pretty new to rifle casting, but I've been pushing a 150 gr right up to 2,000 with Lyman Moly lube and a GC. No problems so far.

lar45

04-02-2022, 12:07 PM

My test rifle is a cutom M98 Mauser built by MBT Custom with a 14twist Krieger barrel chambered in 30-06XCB
http://www.lsstuff.com/pics/cblue/30-06xcb.jpg

with the 30XCB bullet I have gotten great results with 2500+ and Carnauba Blue.
http://www.lsstuff.com/pics/cblue/cblue-30xcb-01.jpg

http://www.lsstuff.com/pics/cblue/cblue-3006xcb-02.jpg

Carnauba Blue gave very little variation for the cold bore first shot flier.
The picture above is for 10 shots.

I also seat my bullets to .005" off the lands instead of seating them into the lands.
I don't know why this gives better results for me, but it does. I've tried it several times with various lubes and seating depths and .005" gives about 1/2 the group sizes of .010" off and seating into the lands.

A note on pushing very high velocities, approaching 2900fps, the lube appears to collect at the front of the gas check and hydraulically swages the shank of the bullet down allowing the gas check to come off once it leaves the barrel.
I plan on seeing if Al will cut me a 30XCB mold with the gas check shank a little shorter to minimize the gap between the gas check and the bottom driving band to see if this will have any effect. I will probably need another rifle with a 16" twist to push those velocities with any hope of accuracy.

Bigslug

04-02-2022, 12:30 PM

Fantastic stuff so far guys!

Regarding twist rate: I'm primarily launching this quest for off-the-shelf .30 caliber rifles, so 1-10 as the norm with 1-12" as the slowest is going to be my most likely playground. While the slower twist makes a great deal of sense, these are double-duty guns that will be shooting Barnes coppers as their hunting loads.

Regarding bullet design: Do you have an opinion specifically on the structure and application of many small lube grooves vs. fewer large ones? I've had good results pushing the NOE/Ranch Dog 178 grain Tumble lube / Gas Check - which was specifically designed for the .308's neck configuration - in the low 2000's. It's a fantastic jug buster with it's big meplat, but not really designed for distance. My "go to" for the .30-06 has been the 311299 GC with Ben's Red, but the groups fall apart and the crown gets plated with alloy vapor as the speed increases. I have the .30 XCB mold, but the rifles it was bought for turned out to be a bust for other reasons, so it has not yet had its fair shake.

Regarding propellants: Larry/Budzilla, I've had fantastic luck with H4831SC with jacketed, though it would not have occurred to me to use it to push cast. Do you think that slower burners like that are easier on the bullet structure, or somehow offer better obturation characteristics?

Budzilla: I too have noted "stout" recoil when ramping things up with the 311299 - about a 200 grain bullet - in the .30-06. My pet theory is that it may have something to do with the fact that we're taking a system nominally designed for a .308 jacketed bullet and feeding it a .310"-311" projectile, typically cast of fairly stiff stuff for the purpose of achieving HV, and that a good bit of violence is going on in terms of chamber pressure as the bullet swages down. Maybe this is where a slower burning powder and a gentler "liftoff" may help?

Regarding lubes: I have not yet ventured into the world of PC. Another tool in the toolbox, though it looks like success can be had with or without it. Forrest r - fascinating that you've tumble lubed OVER PC.

QUESTION: What is your method for tumble lubing over the top of conventional lube? I've only dabbled in that briefly, but it seems like the TL solvents combined with the rolling around and banging into other bullets will dissolve and otherwise compromise the clean fill of the conventional lube groove fill. Otherwise, I absolutely agree that a full-bullet coating of ablative TL can only help with the process.

ANOTHER QUESTION: Have any of the PC-ers experimented with conventional lube on top of a PC'd bullet? Since a lot of PC folks seem to be sizing after PC, this seems like it would be a natural progression that would serve to help keep all the hot gasses behind the bullet - - possibly serving the function of a base wad or filler without taking that actual step.

And for Forrest r, STILL ANOTHER QUESTION: Absolutely fascinating, your results with the hollow-pointed Cramer. I agree that the hollow pointing might be adding significant rigidity to the front end of the bullet making it more resistant to nose slump, but MAYBE another factor is that it's moving the center of mass further back into the driving band section, making for a functionally shorter bullet length that's happier in your 14" twist?

Forrest r

04-03-2022, 07:48 AM

I've been meaning to try different lubes, simply been using up the LBT Blue (hard) I have laying around.

Forrest r

04-03-2022, 08:04 AM

Fantastic stuff so far guys!

Regarding twist rate: I'm primarily launching this quest for off-the-shelf .30 caliber rifles, so 1-10 as the norm with 1-12" as the slowest is going to be my most likely playground. While the slower twist makes a great deal of sense, these are double-duty guns that will be shooting Barnes coppers as their hunting loads.

Regarding bullet design: Do you have an opinion specifically on the structure and application of many small lube grooves vs. fewer large ones? I've had good results pushing the NOE/Ranch Dog 178 grain Tumble lube / Gas Check - which was specifically designed for the .308's neck configuration - in the low 2000's. It's a fantastic jug buster with it's big meplat, but not really designed for distance. My "go to" for the .30-06 has been the 311299 GC with Ben's Red, but the groups fall apart and the crown gets plated with alloy vapor as the speed increases. I have the .30 XCR mold, but the rifles it was bought for turned out to be a bust for other reasons, so it has not yet had its fair shake.

Regarding propellants: Larry/Budzilla, I've had fantastic luck with H4831SC with jacketed, though it would not have occurred to me to use it to push cast. Do you think that slower burners like that are easier on the bullet structure, or somehow offer better obturation characteristics?

Budzilla: I too have noted "stout" recoil when ramping things up with the 311299 - about a 200 grain bullet - in the .30-06. My pet theory is that it may have something to do with the fact that we're taking a system nominally designed for a .308 jacketed bullet and feeding it a .310"-311" projectile, typically cast of fairly stiff stuff for the purpose of achieving HV, and that a good bit of violence is going on in terms of chamber pressure as the bullet swages down. Maybe this is where a slower burning powder and a gentler "liftoff" may help?

Regarding lubes: I have not yet ventured into the world of PC. Another tool in the toolbox, though it looks like success can be had with or without it. Forrest r - fascinating that you've tumble lubed OVER PC.

QUESTION: What is your method for tumble lubing over the top of conventional lube? I've only dabbled in that briefly, but it seems like the TL solvents combined with the rolling around and banging into other bullets will dissolve and otherwise compromise the clean fill of the conventional lube groove fill. Otherwise, I absolutely agree that a full-bullet coating of ablative TL can only help with the process.

ANOTHER QUESTION: Have any of the PC-ers experimented with conventional lube on top of a PC'd bullet? Since a lot of PC folks seem to be sizing after PC, this seems like it would be a natural progression that would serve to help keep all the hot gasses behind the bullet - - possibly serving the function of a base wad or filler without taking that actual step.

And for Forrest r, STILL ANOTHER QUESTION: Absolutely fascinating, your results with the hollow-pointed Cramer. I agree that the hollow pointing might be adding significant rigidity to the front end of the bullet making it more resistant to nose slump, but MAYBE another factor is that it's moving the center of mass further back into the driving band section, making for a functionally shorter bullet length that's happier in your 14" twist?

Larry would be the one to ask about pointed nosed bullets and their affects on accuracy. I remember reading posts about it when they were designing and testing the xcb bullet.

I did testing with the MP hunter bullet
https://i.imgur.com/zaPMUWU.jpg

It didn't matter if the bullet was a fn or a hp, both nose styles performed the same when tested head-to-head with the same loads. As you see from the picture above the nose of that hunter bullet fit the leade of my 308w chamber extremely well (rifling marks on loaded round).

I also did testing with the MP silhouette bullet doing head to head testing with the solid nose VS hp's. Same thing, didn't matter.
https://i.imgur.com/3IJU3TG.jpg

I didn't take a lot of pictures of the silhouette bullets, wasn't impressed and sold the mold after 2 or 3 test runs.

Larry Gibson

04-03-2022, 01:47 PM

"Regarding propellants: Larry/Budzilla, I've had fantastic luck with H4831SC with jacketed, though it would not have occurred to me to use it to push cast. Do you think that slower burners like that are easier on the bullet structure, or somehow offer better obturation characteristics?"

Yes. The time pressure curves are slower. Thus, the acceleration rate is slower so there is less potential deformation of the bullet during acceleration.

Long, pointy, unsupported nose are susceptible to canting in the bore because most have minimal groove diameter bearing surface.

While I have pushed some bullets with bore riding noses [notably the 314299, the 311291 and the 311041] to 2300 - 2400 fps in my 14' twist .308W rifle holding 2 moa accuracy to 200 yards they are not the best designs for better accuracy at even higher velocity. The Lovern designs have always had a reputation for very good accuracy at higher velocities than other designs with pointed or bore riding noses. I got a 311466 mould (152 gr) Lovern Lyman mould and quickly found in my 1 - 10" and 1 - 12" twist 308W rifles it was indeed capable of holding accuracy at higher velocities. The question was, why? An analysis of the design showed it had a short non bearing nose, maximum groove diameter bearing length at 65 - 70 % and multiple shallower lube grooves. During this time I was posting the results her eon this forum and got a lot of adverse interest but also some positive interest. Tim Malcom (goodsteel) worked with Accurate molds and cam up with a 150 gr bullet that showed some promise. However, that bullet also had a longer than needed unsupported nose and one large lube groove. He sent me the moulds, I cast a bunch, and thoroughly tested them.

Most designs, even ones of the last 20+ years, all have lube grooves based on the concepts of what was needed 100 years ago with the lubes available then. With the advent of beeswax/alox lubes in the '50s it was found most of those designs, including the modern ones with similar lune grooves, were "over lubed". Depending on the RPM, the excess lube will get thrown out of the grooves shortly after muzzle exit. If the lube comes off uneven the balance of the bullet is adversely affected. Also, the lube coming off is affected by the air traveling around the bullet and causes further wobble to the bullet.
With modern lubes such as the NRA 50/50, 2500+, 2700+ and similar lubes all that lube in traditional designed lube grooves is not needed. What is needed is "just enough" lube and a soft lube so it will come off the bullet evenly after exiting the muzzle.

Acceleration forces are tremendous when we accelerate a bullet from motionless to 2500 - 3000 fps in just 24 - 30" +/-. The smaller the unsupported smaller diameter of the bullet in the lube groove it is the greater the chance the alloy cannot withstand the acceleration with some collapsing or bending may occur. The deeper the lube groove the smaller the diameter of the bullet is in the lube groove and, thus, the greater that chance of the bullet collapsing or bending, especially with an unsupported or even a bore riding nose and minimal bearing surface.

After thoroughly testing the Accurate XCB bullet in 10, 12 and the 14" twist 308W rifles I found it worked fairly well compared to other traditional bullets but no better than the 311466 Lovern bullet. Tim and I conflabbed with a couple others including Swede Nelson at NOE. I was one of the primary designers along with Tim, Swede and another of the 30 XCB bullet which was designed expressly for HV velocity. The design concepts were based on those factors which we believed would enhance accuracy at HV. The 310-165-FN "XCB" bullet design was finalized with a minimal nose for a decent BC. The front was tapered to fit the 30 XCB reamer [a 30-06 with a tight neck giving .001 clearance with a .310 bullet in neck trued cases with the bullet seated with the GC at the base of the neck. The throat (including free bore and leade) cut to fit the taper on the front of the 30 XCB bullet. The design maximized the groove bearing diameter at 65+ %. I consulted with Swede on the number of lube grooves to use, the width of them and the depth of them. Based on experiments with varied amount of lube in the 311466 bullet needed at HV in 28 - 30" barrels we came up with number and size of the grooves on the 30 XCB bullet to provide that amount of lune, no more and no less. It has proven to be a sufficient amount of lube for velocities up through 3300 fps.

The cartridge for the bullet was originally supposed to be the 30x57 which is a short chambered 30-06. The case capacity was equal to the .308W but it had the body taper to feed well in Mausers and the neck length to hold the lube grooves of a 165 - 170 gr cast bullet in the neck. Bjorn and another did a bit of experimenting with the first 30x57 XCB rifles made. I also did a lot with the 30 XCB in my 26" M70 with 12" twist and my 27.7" barreled Palma 308W with a 14' twist. I found with the slower powders the case capacity of the .308W, and thus the 30x57 was just not quite enough to reach much above 2700 fps. I surmised, based on several thousand test rounds out of the 308W that a case with 100% load density of 52 - 54 gr AA4350 would be just right for 2900 - 3100 fps out of a 30" barrel. So, I ordered up a Broughton 32" barrel with a 16" twist and had it sent to Tim. I sent him a nice CZ-24 M98 action along with 3 formed cases for the 30x60 cartridge. They held (cases formed from Winchester 30-06 cases) 54 gr of AA4350 at 100% load density. Tim put the barrel on the action (he worked his usual magic truing everything up) and it came out at 31". I bedded the action when I got it back and began testing. The results were nothing but astounding. A search of this forum will find numerous posts detailing the results. However, here is a typical 100 yard 10 shot groups. I have also posted a sub moa 11 shot group shot at 600 yards. Additionally you can find the results fo a PD shoot i used the 30x60 on in Montana shooting them at 300 - 500 yards. After 3,000 + rounds testing i settled on 53 gr AA4350 which runs right at 2900+ fps at 48,000 +/- psi.

298507

The 30 XCB has also proven to be an excellent cast bullet at "normal" cast bullet velocities. The 30 XCB is my match bullet for CBA commercial rifle matches using my M70 Match rifle in 308W with 12" twist. Here are 2 five shot and a 10 shot groups for score on the CBA score target at 100 yards [upper left, right and bottom right. Thye bottom left is a sighter target) out of the M70 with the 30 XCB loaded over 2400. Velocity is 1850 fps.

298508

Bigslug

04-03-2022, 06:39 PM

This is all very hope-inducing info Larry! I've got a 31" .30-06A1 with an 11" twist that likes 190gr SMK's and H4831SC, and the XCB mold is already on hand. . .

My personal version of Ben's Red runs with a little higher beeswax concentration for added stiffness (yet still flows at room temp), but the supply is getting low and it's time to mix up or buy a new batch of. . .something. Any suggestions there?

Larry Gibson

04-03-2022, 07:06 PM

2500+

Bigslug

04-03-2022, 07:55 PM

Cool! I found the 2500+ on the White Label site. (I'm SO glad that using a 4-digit number to designate a lube that's bound to be mentioned in discussions of 4-digit muzzle velocities isn't confusing AT ALL ;))

Any direct links to Javelina? Assuming that's a home brew?

Larry Gibson

04-03-2022, 09:04 PM

Unfortunately, Javelina is no longer made. It was basically the NRA 50/50 lube using the type of alox no longer available. White Label's 50/50 is a very close facsimile with the type of alox available.

justindad

04-03-2022, 10:54 PM

That is an excellent question. Unfortunately I have more questions than answers. I have been trying unsuccessfully to develop a 22 Hornet load for use on prairie dogs at near jacketed velocities. Larry Gibson with his 30 cal. XCB 16 twist barrel has achieved the best results I am aware of.

https://castboolits.gunloads.com/showthread.php?439456-Maximum-velocity-with-lead-boolits&p=5364266#post5364266

https://castboolits.gunloads.com/showthread.php?356607-NOE-30-XCB-30x60-XCB-600-yards
Taking stock of all available questions is half of step 1 and wholely step 2 of solving a significant problem. Brainstorm questions, then organize questions in order of likely value.
*
The best decision will be made understanding the risks of being wrong… rather than the assurance of being right.

charlie b

04-04-2022, 07:58 AM

Larry's experience in here encouraged me to start casting for my .308. I wanted to shoot it more and jacketed bullets for it are a bit expensive, especially the 'good' stuff. Unfortunately, mine is a 1-10 twist so it is limited in velocity if I want ~MOA groups. Around 2000fps seems a sweet spot for me with the two bullets I cast the most. The XCB and the Acc 31-210E (Eagan) bullets. I went the powder coating route.

If you consider max vel for 210gn jacketed in the .308 is around 2400fps then I can get close to jacketed velocities with the cast stuff. ~2MOA is pretty 'easy' at 2400fps with the faster twist. But, since I want more accuracy then I load it slower.

If I wanted a cast bullet only rifle (I still shoot jacketed in my .308 at 1000yd) then I would have a slower twist and longer throat. I also toyed with the idea of "Larry's" custom cartridge, a shorter .30-06 (or a longer neck .308) and a 14 or 16 twist barrel. But, I haven't gone any further with it since my .308 is shooting fairly well at this point.

FWIW, with powder coated I still use Hornady gas checks. The simple reason is they crimp well on the bullet. They have to for me since both of the bullets I load have the gas check below the case neck. Don't want it to slip off in the case and lodge in the barrel!!! I also powder coat over the GC so an added amount of 'security' to keep the GC on the bullet.

pworley1

04-04-2022, 08:14 AM

Great information. Thanks to all for posting their results.

Larry Gibson

04-04-2022, 08:54 AM

There are other facets to shooting cast bullets at HV and hold accuracy to less than 2 moa (10 shot groups) which maintain linear group expansion to 300 yards (minimum) than have been mentioned. If you are going to attempt to accomplish that consistently on demand, then;

The rifle/scope must also be capable.

The shooter must be capable.

You must learn how to cast not only excellent bullets but must learn to cast match grade bullets if 1 moa at HV is the goal.

You must understand the RPM Threshold and how to push it up if you're working with faster than 13" twists.

You must understand how to load match quality ammunition and be able to do it.

There are others. It's not difficult once you understand what it takes.

Bigslug

04-04-2022, 09:22 AM

If I wanted a cast bullet only rifle (I still shoot jacketed in my .308 at 1000yd) then I would have a slower twist and longer throat. I also toyed with the idea of "Larry's" custom cartridge, a shorter .30-06 (or a longer neck .308) and a 14 or 16 twist barrel.

Twist rate. . . What did Wyatt Earp say in Tombstone? "That's the damnable misery of it" When you own a bunch of rifles that were optimized for the NRA Match Rifle game as it was played in the pre-AR-Conquest era, when 175 and 190 grain Matchkings were purchased by the 500-count box, my options in this field may be limited.

I'm gonna have to check. . .I think ONE of my .308's may be a bog standard 1-12" (it shot the 175 MK VERY well), but that's gonna be the slowest .30 in the stable. With luck, it may have a longer throat courtesy of being burned out.:mrgreen:

Got the 2500+ lube ordered last night. A few other projects going before the XCB's can be poured in earnest - one of those will be helping my Dad out with a newly acquired .30-40, and the XCB design concepts will likely factor heavily into the base design of a custom mold if it turns out we need one - - this thread is bearing good brain fruit.[smilie=w:

charlie b

04-04-2022, 08:15 PM

I guess I would have to ask, why do you feel the need to push the bullets faster? I can understand if you want to be able to shoot out to 600yd or more. But, when I do my part I can stay under 2MOA at 500yd with a MV of 2000fps (210gn bullet, 1-10 twist). Yes, if I competed, the extra vel would reduce wind drift, making for more points on the target. But, I still shoot for fun :) And figuring the wind hold is something that challenges me.

Larry's points about these being 'match' ammo is also well noted. I take as much care making my cast loads as I do my 1000yd loads with the Bergers and SMKs.

Bigslug

04-04-2022, 11:34 PM

I guess I would have to ask, why do you feel the need to push the bullets faster? I can understand if you want to be able to shoot out to 600yd or more.

Distance is indeed the intention, and getting there with something kinda, sorta resembling the trajectory of a jacketed WWI-WWII service rifle load has much appeal. Just as an example, the Leupold CDS dial on my hunting .308 was ordered for my 130 grain Barnes load. When I'm blasting milk jugs at 100 yards for practice with my 178 grain NOE / Ranch Dogs, I have to ratchet up to the 400 yard setting. Something that tracks closer to that scope or a service rifle's issue sights would be just one goal. Simply not running out of elevation might be another.

Pop and I got the "match ammo process" down very solidly with the jacketed bullets for Highpower, though casting obviously has more nuance. We've gotten sufficiently good at pouring our own to be pretty picky about what we keep and what we melt, and we're pretty cozy in the <2000 fps arena - so the next logical step is to see if we can follow Chuck Yeager.

Larry Gibson

04-05-2022, 09:53 AM

Do a chamber cast of that match rifle with the 12" twist That rifle will be the better choice. If the bore right in front of the leade runs .302 then I suggest the Lyman or NOE 314299. If the bore still runs .300 then the nose can be sized down so it is a tight slip fit. Loaded over RL19, RL22, 4350 or 4831SC I have maintained 2 moa accuracy out of my .308W M70 match rifle with 12" twist at 2250 - 2300 fps. The 311/314299 bullets has a very good cast bullet BC and at 2100+ fps holds sonic to 600 yards. I not had a problem with running out of scope adjustment [my scopes on such rifles are mounted to maximize elevation capability] or with Redfield or Lyman match receiver sights.

Bigslug

04-07-2022, 09:24 AM

Some thinking and questions on lube groove design:

It should be understood that for our purposes, the primary function of bullet lube isn't really "lube", but rather to act as a gasket material to seal hot gas behind the bullet and prevent flame-cutting and leading. In order to do that, the lube has to make it out of the lube groove and to the outer surface of the bullet.

Compression from the lands will squeeze the bullet and displace the lube into whatever void is available. This is much the reverse of the process from the lube sizer that put the lube on the bullet. Some barrels are going to squeeze more or less due to number of grooves and their depth. The initial compression of swaging the bullet to the bore is equivalent to us turning the compression screw on the lube sizer, but we can't turn the screw again if we don't fill all the voids.

Assuming that we had a barrel of infinite length, that pressure on the lube will eventually dissipate as some of it flows into voids between bullet and barrel, and it will reach an equilibrium with the new shape of the rifling-disrupted lube grooves. Hopefully the bullet gets out of the bore before that happens. If the bore is tapered, this pressure will keep increasing, but for most of us, we're dealing with straight cylinders. We know that, typically, there is roughly .01" between the top of the lands and the bottom of the grooves, and our cast bullets are typically .001"-.002" oversize.

My questions then are "How do we - generally - determine how much lube we need?", and also "How do we determine what number of grooves and the width/depth our lube groove or grooves need to be?"

I'm also thinking that MAYBE the centrifugal force of the bullet rotating will have some ability to push the lube outwards, but I also think that, being effectively a liquid, the bullet may rotate and accelerate AROUND the lube, and the lube itself will not really spin.

TurnipEaterDown

04-07-2022, 11:19 AM

I remember reading about cast bullet design, and finding a lube volume calculation tool. Can't remember where, some memory suggests a Dave Scoville article.

Other things I have read taught me that the lube has to be an effective anti-tinning agent. The pressure and relative speed of the surfaces (bullet to bore) tries to create contact, does create heat, and without an effective anti-tinning agent, will attempt to create soldering. Made sense, as I know that friction welding is something we exploit in industry for tube welding and other manufacturing processes.

From my engineering background I can readily believe that the lube distribution mechanisms I have seen suggested are entirely true:
1. Direct pressure on the lube from the rifling form attempting to reduce the lube cavity volume. The rifling cuts into the side of the bullet and intrudes on the lube cavity volume.
2. Pressure from the propellant charge attempting to deform the bullet, across the section at the base of the lube groove (even purely elastic deformation is deformation, and foreshortening of the cavity even temporarily, will make the containment volume less and squeeze the lube)
3. Centrifugal forces on the lube will promote radial motion. Question by bigslug may be valid, but the friction between the bullet and the lube will try (to some extent anyway) to carry the lube with the bullet body as rotation is imparted and spin the lube w/ bullet. How perfectly, I suppose no one knows unless detail math and experimentation would be done.
4. Inertia effects on the lube as the bullet is accelerated. The lube is a separate material, and wants to 'stay at rest', so "stacks up" (creates pressure) on the bottom of the lube groove and wants to flow out.

On this 4th item, I wonder now and then if a beveled lube groove has any benefits in particular instances.

In a practical sense, it all seems to be: lube star on muzzle, you are OK. :)

Larry Gibson

04-07-2022, 11:44 AM

My questions then are "How do we - generally - determine how much lube we need?", and also "How do we determine what number of grooves and the width/depth our lube groove or grooves need to be?"

I didn't know of any formula or rule of thumb when I conversed with on the 30 XCB design but here's what I came up with. I did know from extensive experience over many years with Lovern designs and lee's TL designs that not nearly as much "modern" lube is needed as thought. With the 311466 I had reduced the amount of lube used so that with 2600 fps loads there was just a hint of a "star" of lube on the muzzle. Swede sent me the conceptual drawing for the 30 XCB which had conventional lube grooves. I called him back and we had a lengthy, several actually, conflab on changing the lube groove part of the design. I took a SWAG based on my testing and experience and came up; the lube groove should be twice the depth in the bullet as are the grooves in the barrel with the width of the groove being 4 times as wide as the depth. That meant given .004" deep grooves the XCB lube grooves should be .008 deep and .032 wide. There's always a bit of +/- because of a slight taper to the sides of the grooves and the +/- expansion/contraction of the alloy used needed for the bullets to readily drop from the mould.

Also, from my experience with less lube on the 311466 bullet I knew that it would take two to three such grooves. With that we made the GC shank long enough so there was, with Hornady GCs, an area in front of the GC would be about 2/3 the width of the other lube grooves. The shank was smaller in diameter than the bullet diameter in the lube grooves so the space in front of the GC would hold a similar amount of lube. The two regular grooves were spaced evenly apart on the bullet core cylindrical bearing surface. That concept worked out perfectly as with my standard 2900 fps load in the 30x60 xcb rifle there is just a hint of a lube star on the muzzle after firing.

I have to disagree with your assumption of "the primary function of bullet lube". Historically the use of lube on bullets has been to provide a lubricating barrier between the bullet and the bore. I do agree, in some applications the lube can act as a "seal" but that is in low pressure, low velocity loads. Is it feasible the small amount of lube on the 30 XCB can seal the pressures of 50,000 psi [actually measured] with the bullet achieving 2900 fps in a 31" long barrel? Perhaps we could assume that but what I do know is there is lube deposited all the way from the leade to the muzzle and not hint of leading after even 100+ rounds have been fired with no hint of a loss of accuracy either.

Additionally, a couple members over on the CBA forum have conducted tests of unlubed bullets and found they did not lead at upward of 1800 - 2000 fps. Without a lube to act as a gasket and seal the area around the bullet how do we then account for a lack gas cutting? There's obviously more here to be learned.

Bigslug

04-08-2022, 12:50 AM

There is of course a lot going on that will either seal the bore, or cause a failure to do so.

Our lead itself is something of a fluid medium, and I've often looked at some of the old school rifling profile drawings for early Lee Enfields, and figured they were COUNTING on a lot of squeezing and deforming. In starting our cast bullets a little over groove, we're stacking the odds in our favor for a good seal.

Then there's the whole trailing edge failure problem of too much torque opening up the cleanly engraved impressions on our cast bullets. Gas checks minimize this, as does alloy choice, and certainly Larry's slower twist barrels.

As a gasket material, I think it's fair to say that lube can't do the job by itself - -OUR job is probably best described as minimizing the amount of work it has to do.

Now here's a theory just off the top of my head - - so forgive the cookie if the dough isn't all the way baked: The pressure created by the powder charge against the relatively large base of the bullet is going to crush the bullet into the lands and force the lube into comparatively VERY much smaller voids. Might it be that the pressure of the lube in those very tight spaces EXCEEDS the gas pressure in the bore behind the bullet, thus keeping the gas off the sides of the bullet? As the bullet travels down the bore, the space our powder gas has to expand into increases, and the pressure drops drastically, BUT since our lube has much less space to expand into, it's ratio of counter pressure to the gas may actually INCREASE. . .at least if we figured everything right and designed and fit the bullet properly. This might lead someone to going DEEP down a rabbit hole of designing an integrated system of rifling profile and lube groove design - -assuming the notion isn't totally off base, of course.

charlie b

04-08-2022, 08:58 AM

There are quite a few things about lead under pressure I'd like to know about for certain. The obturation thing and what pressures it happens at for which alloys is one. 'Slump' of a long nose bullet is another. Several theories are floated around but I'd sure be interested in testing of these under controlled conditions.

Larry's statement about the lands causing the force against the lube I think has a lot of merit and, IMHO, is the primary source of lube in the system. This may be the source of the 'extra' pressure Bigslug postulates that keeps gas cutting at bay.

This also makes me wonder why so little lube works. The amount of lube in the grooves of an XCB does not seem like enough to lube the whole barrel. Is the purpose simply to prevent gas cutting? That does make sense to me. The lead needs a 'flexible gasket' along the length of the barrel to account for irregularities. The fewer irregularities the less lube needed.

charlie b

04-08-2022, 09:02 AM

PS one idea I had forgot about. Precision Shooting magazine in the old days (early 80's) had a short series about cast bullets and benchrest shooting. They presented some information that flew in the face of a lot of this. The authors used almost pure lead bullets, without lube, and a slightly oversize polyethylene wad at the base. They experienced no leading. IIRC the velocities were in the 2000fps range.

Father-in-law and I tested this with .357 loads and got very good results as well.

Larry Gibson

04-08-2022, 10:35 AM

Lead paste is a lubricant used in machining; I have some. Thus, pure lead does have its own lubricating effect. However, it's when we add antimony and/or tin to the lead it seems we have leading from the alloy if not lubed? Further testing is probably in order? "Obturation" in the case of bullets is generally thought of as "bumping up" to seal the bore. However, if we push a .310 cast 30 XCB into a .308 barrel there is no "bumping up" but there is swaging down. With a lubed bullet it is generally though the bullet then seals the bore. That is not true. My own recovered bullets and those of an extensive test conducted by Lars and goodsteel positively demonstrated that lubed cast bullets, regardless of alloy or velocity, will swage down and exit the muzzle at a few thousandths less than the groove/bore diameters. In the case of my 30 XCB bullets they exit the barrel at .303 to .305 diameter, not .308.

That is additional proof the bullets ride the bore on a layer of lube. It is also the reason the same bullet, if PP'd or PC"d, can be pushed to a higher velocity and maintain accuracy. There is no layer of lube to further swage down those clad/coated bullets. Thus, they exit at barrel/bore diameter.

As to Bigslug's theory, he might be onto something. Given the fact fluids are not very compressible, a bullet .001 to .003 over groove diameter with large lube grooves filled with lube may be initially "distorted' by the lube when the bullet first is swaged down to under groove diameter. Since a .003 over groove diameter bullet will be swaged down .0006 thousandths can we assume there is also swaging distortion of the bullet in the lube groove also? Considering sizing a TL bullet down .006 w/o lube filling the grooves will "wipe" the grooves away. Yet if we fill the TL grooves with lube and then size there will be a greater elongation of the bullet which will still have lube filled grooves [I have done this].

As to bullets "slumping" under acceleration, years ago I shot on a range where, in the winter, considerable snow would be behind the 100 yard target line. As there was no berm the bullets were slowed and stopped in the snow. When the snow melted the bullets were easily recover, almost undamaged. I was trying to get higher velocity out of the 311284 and 311291 with 4895 powder. Only the grooves above the GC and the first lube groove were lubed with javelina lube. I was pushing them to 2300 fps (I had an Oeler chronograph back then [mid 70s]). I was not able to get match grade accuracy with either bullet above 1950 fps that would hold 2 moa or less at 200 and 300 yards. Recovering bullets when the snow melted, I noticed some of the 311284s and 311291s had rifling marks on one side of the nose and not on the other. There also was some compression/collapsing in the unlobed front grooves on those bullets. That indicated the inner bullet column had collapsed or bent allowing the bore ride nose to slump off to one side of the bore enough the rifling engraved it deeply. I believe there is a picture of such in the NRA cast bullet supplement(?).

Back then I did not understand the adverse effect of RPM or the potential benefit of slowing the acceleration rate down with a slower burning powder. I had much to learn back then.

charlie b

04-08-2022, 11:09 AM

Thanks Larry.

To me, if only one side of the bullet had marks, then it was 'tilting', which is another issue with long bore riding bullets. I have seen accuracy issues that I attributed to this when using a bore rider that was less than bore dia. The ones I use now, powdercoated, are an interference fit in the bore. If I remove an unfired bullet there are marks from the rifling around the nose of the bullet. I have not been able to recover one intact.

The tilting would cause more stress on one side of the bullet which would do weird things to the other parts. I'd still wonder if this was true 'slumping' or just the result of a bullet slightly tilted in the bore.

And I still have a lot to learn :)

centershot

04-08-2022, 01:17 PM

The tilting would cause more stress on one side of the bullet which would do weird things to the other parts. I'd still wonder if this was true 'slumping' or just the result of a bullet slightly tilted in the bore.

And I still have a lot to learn :)

"Slumping", bending, call it what you will, we know it happens, unfortunately. The cause, at this point is anyone's guess. Larry's trials with an empty lube groove would indicate the bullet is bending under pressure. The question in my mind is, with all lube grooves full, why are bore riders more difficult to get good groups from? I've not been able to get ant bore rider to group as well as the 311041. That bullet is a real star amongst .30 caliber bullets, IMO! I've gone as far as nose-sizing .303 bullets down to .300 noses, then sizing the bodies. Still no cigar! I've been using 94-3-3 alloy as I intend to hunt with these rounds, but may need to abandon higher velocity and stay with the softer alloy for my purpose.

TurnipEaterDown

04-08-2022, 02:03 PM

So, here are some thoughts that may help:
Pure lead makes a pretty lousy solder. Pure lead also oxidizes more easily than most alloys of lead we use in bullets. Oxides on solder surfaces make soldering more difficult.
If the writing I read at one time that good lubes are also anti-tinning agents, then those three things above may help explain the observation stated by Larry that leading is worse w/ alloys.

Lead isn't unique in depositing in a bore, obviously copper does this too. Jacketed bullets are almost never lubricated as we do w/ lead alloy bullets. Metallic deposition in a interface like that with a bullet in a bore is assisted by friction, think of an aluminum piston in a cast iron cylinder bore, so the statement that lube acts as a lubricant probably shouldn't be construed to be understood that it serves no other function, it most certainly can.
The piston-cylinder interface in an engine is a good analogy in many ways for a bullet in a rifle bore, and it always used to be that when doing a compression test on a worn engine you did it "dry" and "wet". The additional oil would create higher cylinder pressure readings on a badly worn bore-ring interface because as a viscous fluid it would help to seal the ring against the bore over areas where the ring had low residual tension & contact.

What Larry states about recovery of undersized bullets is quite striking.
If the bullet was bigger than the bore before firing, and smaller afterward, it must have experienced Plastic Deformation in the trip down the bore. Nothing outside of the bore would compress the bullet radially as required to produce this observation. The forces also had to have been from something more than physical interference with the riling & bore themselves.
Bullet materials can be deformed elastically, and in a plastic manner. Elastic deformation is removed when the force is removed. Plastic deformation is that formed when the stresses exceed yield, and is permanent. Plastic deformation comes After elastic.
Point being: for a 0.308 bore (assuming a good quality barrel w/o gross internal constriction somewhere) to deform a bullet such that when it is recovered the bullet measures 0.305, it was About to leave the bore somewhat even Smaller than this 0.305. There is Some elastic deformation that will be relaxed After leaving the bore. The plastic deformation doesn't recover, and can be measured. The bore & rifling didn't create that plastic deformation, something acted inside the barrel to gain this additional plastic deformation, greater than that possible by teh rifling & bore. I suppose hydraulic compression is a reasonable theory.
To initially test the theory of hydraulic compression, it isn't necessary to run a physical experiment. An initial level of hypothesis testing can be done by considering the volume of lube that would be required to gain the proposed amount of compression on the bullet (i.e. bearing length * 2 pi R * this ~ 0.003" compression observed by Larry), and comparing this to the lube volume theoretically available via displacement of lube from the grooves under two assumptions. 1) lube displaced simply by intrusion of nominal rifling form in the lube groove, (2) total volume of lube in the grooves prior to firing.
If the volume of lube required to surround the bullet and squeeze it this 0.003" (there would actually have to be somewhat more than 0.003") isn't possible by emptying the lube grooves entirely, then the compression can't be achieved by this theoretical mechanism alone. If the total volume is sufficient, but that available by simply the rifling intruding into the lube groove is, then the theory is potentially valid.

Nose slumping / tipping.
The bullet would classically be considered a rigid body, for terms of Physics, but it really isn't. As noted, metals yield, and therefore the bullet is non rigid. This can be a useful observation:
For the bullet to accelerate, all of the bullet will accelerate, so: imagine a cut section just at the base of the nose and calculate the force on the base of the nose (bore diameter) to accelerate the mass of the nose at the same rate as the entirety of the bullet under the simplified assumption of rigid body bullet with an instantaneous acceleration rate produced by simple calculation of F=m*a where F = P*A and P= peak chamber pressure. Once F is then determined on nose section, reconsider the nose as a cylindrical column and look at simple calculation for compressive yield, or even column buckling. If you can't yield or buckle the nose section by assumption of acceleration under peak chamber pressure, then it is something else, like tipping.
I do remember there were shadowgraph pictures of bullets somewhere (maybe something in old Speer manuals, or Lyman, or...??) I looked at that did show exposed nose deformation in jacketed bullets shot at high pressures, so if pure lead is used, the nose section heavy enough an acceleration great enough, deformation by accelerating forces is possible.

Larry Gibson

04-08-2022, 05:56 PM

"Slumping", bending, call it what you will, we know it happens, unfortunately. The cause, at this point is anyone's guess. Larry's trials with an empty lube groove would indicate the bullet is bending under pressure. The question in my mind is, with all lube grooves full, why are bore riders more difficult to get good groups from? I've not been able to get ant bore rider to group as well as the 311041. That bullet is a real star amongst .30 caliber bullets, IMO! I've gone as far as nose-sizing .303 bullets down to .300 noses, then sizing the bodies. Still no cigar! I've been using 94-3-3 alloy as I intend to hunt with these rounds, but may need to abandon higher velocity and stay with the softer alloy for my purpose.

I believe the reason most bore riders are more susceptible to "bending" is their short bearing surface. Bearing surface is that length of the bullet that will be groove diameter or larger going into the barrel. I use a percentage figure by dividing the length of the bearing surface by the length of the bullet. Bullets with 60+ percent bearing surface do not bend, slough or whatever. Obviously, the bearing surface portion of the bullet is in the rear of the bullet. Most bore riders are designed for the shorter necked cartridges such as the 308W. The design concept was to have the GC at the bottom of the neck with all the lube grooves and drive bands inside the neck with the front drive band just touching the leade. Thus, the heavier the bullet of such the longer is the unsupported nose. Yes, the bore [surface of the lands] may give some support but there is usually more groove area to the bore which is not supporting the nose. Hence, the bullet can bend because a long heavy nose has leverage to bend into the grooves on one side of the bore.

My 311041 has just over 65% bearing surface and has proven to be accurate at higher velocities along with the 311291 (55% bearing surface) over such bore riders as the Mp 30-180 and the 311/314299. Older designs with a scraper groove in front of the front drive band such as the 311284 and 311334 are very prone to collapse and bend in the much smaller column in the scraper groove.

Having a larger bearing surface percentage is one of the keys to a HV cast bullet design.

charlie b

04-08-2022, 07:47 PM

I wonder why I get better groups with the long bore rider than I do the XCB and similar bullets? Lots of bench rest folks seem to agree with me, and, some don't :) And, it is a .308 with a 'short' throat that I am working with.

I understand all the physics involved and material stresses, since I was a licensed mech engineer who worked on moving metal with high explosives and lasers. I'd just like some real data instead of theories about why a result is the way it is.

I've worked with softer bullets that were 'upset' into the grooves of the rifling, sealing being done by a wad behind the bullet. I could understand if the long bullets were upset into filling the grooves since the pressures and inertia seem to be high enough. I'd just like some data to confirm things.

Larry Gibson

04-08-2022, 08:55 PM

I wonder why I get better groups with the long bore rider than I do the XCB and similar bullets? Lots of bench rest folks seem to agree with me, and, some don't :) And, it is a .308 with a 'short' throat that I am working with......

The bench rest guys (assuming you mean the CBA guys?) are not pushing those long bore riding nose bullets to HVs of 2000 - 3000 fps nor do their loads generate the pressure required for those higher velocities with the attendant higher acceleration rates. The BR guys push them at 1400 - 1800 fps +/-. Not hardly fitting the parameters of "The Components of Going Faster" as in this thread. I also shoot those long bore riding nosed bullets, the 314299 in particular with some very good groups in CBA competition in a military rifle category. However, the velocity is 1850 fps. I also shoot the 30 XCP in a commercial rifle category out of my match M70 308W but, again, the velocity is 1850 fps.

You can drive a Farari around all day long with cheap retread tires on at 50 MPH. However, at 160+ MPH I don't think the cheap retread tires would work so well...... Same difference with cast bullets. What happens during acceleration to a cast bullet at 1400 - 1900 fps is a lot different than what happens at 2000 - 3000 fps.

TurnipEaterDown

04-08-2022, 09:23 PM

"Charlie b", not sure that my comments were in any way mistaken from my intended purpose, but if they were, my apologies.
I too am a Mech Eng, and have been for 31 years. Mostly testing, issue resolution, and lately project management. I have personally reviewed over 30,000 reported test observances of potential failure, and managed through resolution over 1500 validated design problems.

I am probably a bit like one of Pavlov's dogs, and when I hear something along the lines of 'I wonder', or 'I find it puzzling', I sort of hear a bell ringing inside my head and try to 'help'. If my thought starter comments were taken in a manner that wasn't at worst benign, again I apologize.
I know that my urge to jump in and help sometimes makes my wife want to grab a blunt object...

I wonder if the model of the hydrostatic wedge for lubricant in a rotating journal bearing could be applied to the bullet lube being drawn out of the lube groove and doing it's work on the side of the bullet, and if this would offer insight to the potential pressure of the lubricant on the bullet body. It just strikes me as interesting what Larry said about measuring recovered cast bullets and finding them smaller than the bore size.
I am myself also now pondering if anyone ever designed a bullet with just enough driving band at the front to get the bullet rotating w/o significant skidding, then the lube groove, and then a relatively long no lube groove base. Seems like this would best place the lube cavity to meet needs of function, offer the ability to minimize the quantity of lube required, while potentially making engraving length (bullet body) to cartridge neck length more forgiving.
Not that minimizing lube is any real necessity, it's cheap, but it might be something interesting to learn from in terms of lube function.

charlie b

04-08-2022, 10:27 PM

Larry, you are right and bring up something else I have wondered. How much pressure/acceleration does it take? I've maintained good accuracy up to the RPM limits. For me that has been around 2200fps. I guess I need to 'break out the books' and do some calculations. FWIW, I use Lyman #2 alloy.

Turnip-Not taken in offense. You bring up an excellent point on the performance of lube on high speed bearings. The bullet velocity and spin rate certainly qualify there. I seem to remember such a discussion in the BPCR arena about that.

I have the added unknown of powder coated bullets. Does the polymer act like a bearing lubricant at all? I suspect not. Maybe that is why the closely fit bore riders do well for me? Added toughness increases the overall strength of the lead alloy?

I was interested in the photo of the bore that showed streaks from a PC bullet at higher speed. Was that due to friction heating or something else? May have to invest in a borescope. :)

charlie b

04-08-2022, 10:43 PM

Forgot...Larry, have you measured the pressure differences between the 2700fps loads and the 2000fps loads?

Bigslug

04-09-2022, 10:58 AM

Larry, your observations of bullets getting skinnier on firing are pretty thought-provoking. . .

Because of the big kick in the butt the bullet is getting from the powder charge, the bullet obviously can't elongate backwards.

The drag of the barrel against the front of the bullet would tend to prevent, or at least restrict, the bullet elongating forwards.

Lube getting squeezed by rifling to form a barrier between the bullet and barrel wall would then seem to be swaging the bullet down a couple thou, and the main place that compressing lead would have to flow into would be the lube grooves. This would then decrease the volume of the lube grooves, so it seems that MAYBE the lube is providing its own force to pump more of itself out of the grooves.

298811

I got Dad back home from the range yesterday and we fired up the pot for some XCB's. Going by the hardness range recommended earlier in the thread, we selected a mix of 2-1 linotype and Lyman #2 to hopefully get us about 19 BHN. Unfortunately, the brass NOE mold seems to cast them a little puffy at .312", with the nose dimensions correspondingly bigger as well. It remains to be seen how well they fit in the chambers of the .308's and .30-06's, but the good news is I may still have a place for them:

298812

I had my P14 along yesterday for some giggles, and as we started measuring the slugs out of the mold, we started thinking "Hmmmm. . . .303 British, maybe?" I've got to review my data on the No.4 and No. I MKIII, but this one at least slugs at .312" and pins .303", so it seems a likely place to explore a lot of the very things this thread is discussing.

Larry Gibson

04-09-2022, 12:37 PM

Forgot...Larry, have you measured the pressure differences between the 2700fps loads and the 2000fps loads?

In 308W tests of the 30 XCB bullet in my M70 target with 12" twist and my M98 Palma with 14" twist I used different powders [4895, 3031, RL7] for the low end velocities and slower burners [4350, RL19, H4931SC] for the top end velocities.

At 2000 fps +/- the pressures run 28 - 30,000 psi

2700 fps +/- the pressures run 48 - 50,000 psi +/-

In the 30x60 XCB rifle with the 30 XCB bullet my standard 2900 fps load of 53 gr AA4350 runs 50,000 psi +/-

At 3100 fps in the 30x60 with the 30 XCB bullet the psi runs 54,000 +/-. I began getting flyers above 2950 fps and accuracy really went south at 3000+ fps. The reason I discovered was because the GCs were coming off immediately on muzzle exit. I discovered this the hard way when the Sky Screens were shot. I was fortunate to recover a GC from inside of a Sky Screen. It showed melted on alloy in the inside of the GC cup. Apparently, the shank alloy was melting from friction and/or the heat of gas. Obviously, at 3000 fps + a GC all by itself can be very dangerous at close range :shock:

298814

298815

Bjorn had a 30-06 XCB rifle made with a 17" twist and achieved 3,300 fps with close to 2 moa accuracy as I recall. Of course I did not pressure test those loads.

Larry Gibson

04-09-2022, 12:52 PM

Bigslug

I'm not sure of the exact mechanics of how/why the lube works. Obviously TurnupEaterDown's pay grade is above mine on that subject. What I have learned is, with modern lubes, is how to make it work. Interesting discussion and I am learning the how/why....I think...:veryconfu

That P14 looks very nice. I have a Ross M10 303 I use to test 303 ammo in. Amazing what the locked breech and 29" barrel can do for velocity with above SMLE pressures. I have pushed a .312 Hornady SP to 3,000 fps while staying under 60,000 psi. Not good for a SMLE, No 4, Martini or RB but in the Ross and P14 it is interesting.

GLynn41

04-09-2022, 02:19 PM

can this thread become a sticky

Bigslug

04-09-2022, 02:35 PM

Well, it turns out we're in a pretty good place for testing a number of things here. . .

Dad tried one of the "fat" (.312") hard alloy bullets we cast yesterday in a new Criterion barrel on an M1903 and found it chambered just fine. He also found a bunch that we cast out of WW+2% at .311" which we poured for an Ishapore .308 that turned out to be a bust for handloading due to an excessively over-diameter chamber.

So we're good with a couple different diameters and hardnesses. He's got this newly-acquired 1895 Winchester in .30-40 that he needs to fire form his brass in. Seems as good a place as any to try out the 2500+ lube and the softer WW+2%.

The P14 can undoubtedly be pushed, but the nice thing is that replicating a sight-matching MKVII service load equivalent for any .303 shouldn't require going off the reservation. For sure, these concepts will get wrung out thoroughly in the "beast" actions before we apply them to the lighter, rear-locking Lees.

charlie b

04-09-2022, 05:41 PM

Thanks Larry. The gas check thing is interesting. If it was that hot and you didn't have leading that means the lube is working well under some adverse conditions.

I was going by the Lyman load data, which put me near 45k cup with the XCB at 2200fps. I don't have a good reference on the 210gn at 2200fps, but, 2400fps with 200gn is listed as 50k. Hodgdon max for a 210gn Berger is around 2400fps at 60k depending on powder. Yes, I know cup and psi are different :)

Will do some calculating on pressures and intertia forces on the bullets.

Bigslug

04-09-2022, 07:55 PM

charlie b

04-09-2022, 07:58 PM

Not quite but good try! LOL

It does raise that age old question of how hot does a bullet get as it goes down the bore.

Bigslug

04-09-2022, 10:58 PM

It does at that. My thought was that Larry's check popped off in the bore which allowed for catastrophic gas blow-by which plasma-torched the base and sides of his bullet. That's about the only way I can fathom dumping enough energy onto a bullet to melt it in 2 feet of barrel and the couple of microseconds its travelling down it.

If the bullets are being squeezed down in diameter by this boundary layer of lube we're discussing, the sudden absence of a gas check would be a miniature version of the Challenger's O-ring failing.

Now HERE is a weird one to contemplate: are land and groove sections being compressed equally by this "Lube Force", and is it sufficient to reduce the functional grip of the barrel on the bullet?

There is MUCH here that we do not yet understand. . .:veryconfu

Forrest r

04-10-2022, 04:41 AM

IMHO:

Hydraulic compression is the leading factor that contributes to a cast bullet accuracy or inaccuracy. These are not my photo's, I copied and kept them because they speak volumes about the forces that are applied to cast bullets. A picture of a rifle bullet's base that had a filler used on top of the powder.
https://i.imgur.com/b4GplaC.jpg
Same bullet/same load without the filler.
https://i.imgur.com/fTgTqfa.jpg

Huge difference between the 2 bullet bases and impressive what the forces applied to them did. Another photo that's not mine, it was sent to me by a member on this website. We were discussing square lube grooves VS round. As you can clearly see all the recovered bullets show compression. The compression of the lube groove causes the lube to become pressurized, hence hydraulic pressure.
https://i.imgur.com/M8QJ3DM.jpg

To me pc coating is just that, a coating & more pointedly a plastic jacket. I've never viewed it as a lube & use coated bullets as a double check for bullet design failure. I've showed these pictures before, this is a hb swc that I put a hollow point in to be used in a 44spl snubnosed revolver.
https://i.imgur.com/FTFbMo6.jpg

A side view of that same recovered bullet.
https://i.imgur.com/Swqedh0.jpg

While not the clearest picture, it has a lot to say. It shows extreme compression along with the hollow base kept expanding after leaving the bbl. What I found most interesting about that picture is that my pc coating failed. The nose of the bullet still has the pc coating and as you can see. Easily passed the smash test. The bullet's body on the other hand, didn't so as well. The pc coating was under cured and the extreme pressures exerted on the part of the bullet that comes in contact with the bore came off.

What you see in the picture above with the bullets body and the forces that were applied to it is the same reason the traditionally lubed/sized bullet failed under high pressure/high velocity.
https://i.imgur.com/I2jt2AW.jpg
https://i.imgur.com/y5CttId.jpg?1

I took those traditionally lubed bullets pictured above and added a coating of 45/45/10 tumble lube to them and re-tested.
https://i.imgur.com/QCvbTnt.jpg?3

While not the best accuracy, the bullets went from a shotgun pattern to 2" groups.
https://i.imgur.com/x4M2uh5.jpg?1

This shows why you want enough lube in the lube groove. The hydraulic pressure forces the lube forward protecting the body of the bullet from being deformed where it's compressed against the walls of the bbl. If a 18,000+psi/1000fps load can strip the pc off of a cast bullet. A 40,000psi/2600fps cast bullet has a lot to deal with.

The other extreme is cast bullets like these, the mp hunter & mp silhouette
https://i.imgur.com/zaPMUWU.jpg

Both of those bullets have huge lube grooves that do 2 things. Put massive amounts of lube forward and causes inaccuracy from being sized down like larry described with his recovered bullets. The skinny stem that's left in the lube groove is too small to handle any real high rpm's/rotational torque. I came to these conclusions because with both bullets traditionally lubed/sized I couldn't go over 2200fps in a 1 in 14 twist bbl and maintain accuracy. Up the load & up goes the pressure creating hydraulic compression to the bearing surfaces of the bullets body. Both bullets when pc'd could run up to +/- 2400fps before the skinny stem holding the bullets base would fail causing accuracy to go south.

While lube and hydraulic pressures aren't the cure all answer to everything. They play a huge role in accuracy when it comes to high pressure/high velocity cast bullets.

DonHowe

04-10-2022, 07:05 AM

There are quite a few things about lead under pressure I'd like to know about for certain. The obturation thing and what pressures it happens at for which alloys is one. 'Slump' of a long nose bullet is another. Several theories are floated around but I'd sure be interested in testing of these under controlled conditions.

Larry's statement about the lands causing the force against the lube I think has a lot of merit and, IMHO, is the primary source of lube in the system. This may be the source of the 'extra' pressure Bigslug postulates that keeps gas cutting at bay.

This also makes me wonder why so little lube works. The amount of lube in the grooves of an XCB does not seem like enough to lube the whole barrel.

FWIW,
ALL materials are plastic ("fluid", elastic) under pressure. It's just a question of which
material and how much pressure is required. This elastic property is quantified by what is known as "modulus of elasticity"

Incidentally, even your rifle's barrel, receiver and bolt are plastic under pressure.

nueces5

04-10-2022, 08:28 AM

Fantastic stuff so far guys!

QUESTION:

ANOTHER QUESTION: Have any of the PC-ers experimented with conventional lube on top of a PC'd bullet? Since a lot of PC folks seem to be sizing after PC, this seems like it would be a natural progression that would serve to help keep all the hot gasses behind the bullet - - possibly serving the function of a base wad or filler without taking that actual step.

Hello, I have been trying to upgrade my groups to HV, so on PC I tried to use lube.
At first, a simple lube, made by me, and then I got orange magic, since here in Argentina I can't get anything else.
In my case, I noticed a notable difference when I added a slow powder such as RL19 to the lubricated PC boolit.
That combination made the 314299, bhn 20 with pc and gaschek hornady less than 1 moa at approx 2400 fps on my mauser 1909. Unfortunately it went to 150 mts and I don't have any more RL 19 to continue testing.

TurnipEaterDown

04-10-2022, 12:24 PM

Pretty interesting recent adds.
Apologies for doing what I am about to: replying to a couple older entries in post along w/ new, but got engaged yesterday evening and then had some computer issues.

My first thought about Larry's Oehler was: Bummer, you can't get eyes (sensors) any more, so have to find some. Least last I checked, they had stopped supplying.
Next thought was: I suppose I was lucky, as one GC recently only nibbled my orange sunshade and another nicked the black side piece on mine. I use cast bullets to evaluate suitability of powders when going off the reservation. I had assumed my almost miss was because I used bullets w/ a defect at the base that caused crimp issue w/ the GC. Now, not so sure. Maybe I keep cast bullets away from my Oehler if >2200 fps or so...

Next thought was, it wouldn't be necessary for the hydraulic pressure of the lube to force the GC off. Certainly the lube will most likely get into that interface between the lead body & GC, because every bullet I ever saw w/ a GC does have some defacto lube groove formed at the leading edge of the GC which would likely promote upsetting of the interface by lube under pressure. But if the theory (seeming to be getting more & more support now) is good that hydraulic forces are squeezing the bullet, then, As it squeezes the bullet radially, the GC will have an opportunity to lose contact. Under this theory the contact between GC and shank will be lost because the bullet body is easier to squeeze than the copper GC (stress/strain curve comparison of the lead alloy and copper alloy). Getting Enough deformation of the bullet body to loosen the crimp on the GC is perhaps questionable, but it should be very possible: Larry saw 0.003 compression of diameter, and I suspect that the crimp is in this range or less. Once loose, it very well would try to separate at the muzzle (probably held up to the bullet base in the bore by gas pressure) due to aerodynamic turbulence & possibly muzzle gas turbulence. Probably loosing a crimp on GC is evidence that the bullet body is compressed if you don't even recover the bullet. Of course, not every GC is crimp on, and I don't know what Larry used. Hornady are.

Subequent photos by Forrest r show more interesting things. Some supportive.
The first set of his photos, bullets using filler and no filler I think are interesting primarily because of what is shown on what used to be the bullet side walls next to the base, not at the base. I am always suspicious about the argument 'look: the base is pitted'. The base will certainly also get powder granules pushed so hard into a soft lead bullet base by combustion gases that the indents could look like gas pitting, but I have noticed before a difference in the pits from ball vs. stick powder (IF I rememebr right), so I think it's sometimes at least granule impressions. However, his pictures show damage on what used to be bullet sides that goes away w/ the filler. I think the filler just gets compressed against the bullet base an makes a form of GC.
Which reminds me of a product by CF Ventures called a wax GC, that I never had much luck with. I wrote that off to not trying very hard. Maybe it was counterproductive.

Forrest r's photos of multiple recovered SWC bullets vs. their virgin twins Clearly show column compression of the reduced shank diameter where the lube groove is cut into the body. Absolute proof that collapse of this shank portion (as a column) IS a lube pumping mechanism. Maybe deep grooves are not so good for high combustion gas pressures.

His photo of a HB SWC having been recovered w/ a flared base is highly suggestive to me that when fired the muzzle pressure of that load was enough to create what is displayed. It can't flare like that inside the barrel, and I strongly doubt that it did that when the bullet stopped (apparently through nose first impact), as the deformation shape is wrong.

Two more passing thoughts I had before coming back to the computer are that we Know:
1) That lubricants in a barrel can produce very high pressure -- probably more than me have seen rung 22 RF barrels, and I was always told that this happens from excessive oil left in the bore before firing, given someone didn't jab it in the water or dirt first
2) The swaging folk will tell you that it's not such a good idea to swage down commercial bullets to an odd size, it's better to bump up. This is because the jacket is more elastic than the core and so springs back more creating separation between jacket & core. I learned this when I tried sizing down some jacketed 0.430 bullets to 0.427 in a cast bullet sizing die. The cast bullets size to 0.427. The jacketed come out 0.428-ish. Probably created a loose fit in the final product, but probably also didn't matter as when it hit the rifling everything was squeezed together again. This is on the "how to loose a GC" discussion.

I don't think anyone here would doubt that an undersized bullet will make for lousy groups.
So, if/when squeezed, it is probably key that the lube volume and muzzle speed/pressure is high enough to keep a viscous lube "sabot" around that bullet to get good release & accuracy.
So, it could possibly offer a path to test that: identical high speed/pressure lubed bullet loads in a long (26+) inch barrel, and short (15 ish) inch barrel. Is the short barrel more accurate than the long? Could be valid way to gain insight as long as there is enough lube to keep the long barrel w/o lead at the muzzle.

Hope I didn't make a typing / thought error here. Trying to reply quick before running off for things...

Larry Gibson

04-10-2022, 12:31 PM

The photos of Larry's brutalized chronograph are a pretty good cautionary tale - especially in the context of the direction the conversation has gone on lube dynamics.

A gas check carefully fitted to a clean base and AGRESSIVELY attached would appear to be key, ESPECIALLY in light of my hypothesis that lube pressure in the narrow spaces it is allowed may be greater than the gas pressure behind the bullet. If that theory is right, the lube will be acting much like high-pressure steam and seeking ANY opening it can force itself into. If there's any way the pressurized lube can get between the check and the bullet base, that gas check is coming OFF.

Additionally, working with Larry's observation of the snow-captured bullets being sized down below barrel diameter (again, theoretically by compression by lube), it raises the interesting question of the gas check resisting that lube compression more than the bullet. There might be something to creating a more homogenous bullet assembly by annealing the gas check so it is closer to bullet alloy hardness, or selecting and treating the alloy to match the check's malleability.

Just theory spewing from my public-educated brain, but maybe there's enough there to make one of the engineers go "AHA!":drinks:

The barrel of the 30x60 rifle is 31", closer to 3 feet than two feet.

The bases of the WQ'd #2 alloyed 30 XCB bullets were all anally inspected for any defect and to ensure they were flat. If you're going to push the HV spectrum like I did and get the accuracy results I did, you'll have to do the same.

The Hornady GCs were seated to the shank of the 30 XCB "as cast" at .3105 in a 450 with a .311 H&I die. Then the bullets were lubed in that same H&I die. The bullets then were sized in a Lee push through hone to size at .3105.

The Hornady GCs were tried out of the box, annealed and even super glued on.

Same results; GC of some, not all, were coming off right out of the muzzle. At 2950 fps only 1 or 2 GCs would come off, sometimes. At 3100 fps 3 - 5 GCs out of 10 shots would come off. The GGCs that did not come off went into a 2 moa or less group. It was probably 1 - 5 out of 10 shots that would lose the GC with the higher than 2950 fps the more GCs in a 10 shot test would come off.

At 2900 fps no GCs come off and accuracy runs 1 - 1 1/2 moa out to 600 yards with 10 shot groups. 3100 fps was the maximum velocity I was able to achieve in the 31" Broughton barrel given the 30x60s case capacity.

I'm more inclined to believe the friction heated the GCs enough to melt the alloy next to it. If you've ever pulled targets or had occasion to pick up a jacketed bullet that has just been fired, you'll know (probably from burned fingers) just how hot they get from friction in the barrel. My 31" Broughton 16" twist barrel has 3 grooves with the width of the lands and grooves being equal. The groove depth is .004. I believe Bjorn achieved 3300 fps w/o GC loss because his 17" twist 30-06 XCB had 4 lands and grooves which were not of equal width. Hard to say if the barrel or cartridges made the difference though, can only theorize but there was never any indication on recovered bullets of a gas blow by, but only the melted surface of the shank on some. It was hard to recover bullets w/o sever deformation at that velocity at close range. Thus, I was using a pulpy wet pack bundle at 300 yards and given the inaccuracy or those that lost the GC, hitting the bundle was not assured with those shots. I had a cardboard with a 1 1/2"x 3" slit in it placed 15' from the muzzle to shoot through so I would know which bullets had lost the GC because those lost GCs would hit the cardboard. With 20 shots fired at 3100 fps I had 7 that lost the GCs and recovered 12 bullets out of the wet pack. Of those 12 recovered none retained their GCs upon impact and penetration. There were numerous GCs found in the wet pack indicating many of the bullets retained the GC in flight to impact. However, Of the 12 bullets recovered 2 of the bullets had GC shanks that the surface was melted off. My assumption, based on the test, was they were the two bullets that lost their GC on muzzle exit. That is indication/assumptions of the "why" I believe it is friction in the barrel causing the GC loss.

charlie b

04-10-2022, 07:15 PM

Yep, everything has a yield point. And everything is elastic below that. And most engineers refer to it as Young's modulus. :)

Unless bullets are fired into a medium that does not cause upset of the bullet, then the resulting bullets are not really proof of much except their terminal effects on the 'target'. You can get information from them sometimes, such as the condition of the grooves and if there is 'slipping', relative performance of the lube grooves (possibly), etc.

Forrest, the hammer test, while useful, is not a comprehensive test of the PC/process. Here is what is left of a 210gn bullet fired at 200yd into a bank of sand at ~2000fps along with a before picture.

298856298857

I remember in the past many folks attributed the 'blowing up' of HV jacketed bullets to cores that melted. PC won't help at that point. The cure temp is only ~400F and it only stands up to temps just a bit over that (there are some specialty coatings that go higher). Of course, lead starts to melt just a bit above that so kind of a moot point for PC. There are many PC folks who have melted bullets in the oven while curing the PC at too high a temp. If a bullet is heating in the bore
to over 500F then it is probably melting.

That brings up another point. At these higher speeds are the lubes 'insulating' the bullet a bit, or is the lower friction due to the lube reducing the rate of heating? If that is the case (likely?) then Larry is pushing over that limit. Would more lube assist in that in some way? Or is that just way past the limits of the lead bullet? Or, is that the point where we need to adjust the alloy, or add some copper?

That also brings up paper patching as a possible alternative. It has it's own 'difficulties' when dealing with bullet accuracy.

charlie b

04-10-2022, 07:26 PM

TurnipEaterDown

04-10-2022, 09:56 PM

There no relative rotational motion between the bullet and rifling, so twist rate should not matter in terms of friction heating. The bullet gets spun pretty fast, but relative to the rifling twist, the bullet is static from a rotation perspective. It is however sliding the whole time down a nice dry steel bore on a jacketed bullet, w/ high normal forces from the bullet to the bore due to pressure during the time of acceleration trying to squish that nice cylinder into a flat pancake, with the bore keeping everything in shape. pretty rough trip, and I do believe it probably gets fairly toasty.

M-Tecs

04-10-2022, 10:02 PM

I've never heard or seen of a jacketed bullet blowing up at the muzzle. Normally they blow at the 40 or 50 yard mark. Either it takes some time for the bore friction to penetrate or the air friction adds to the bullet heat.

Bigslug

04-11-2022, 12:38 AM

Making good progress in the "Vehicle Assembly Building" and getting closer to rolling the crawler out to Pad 39A.

298864

Innit cute? :mrgreen:

Got a couple more questions moving forward:

1. Castings with the @19BHN alloy settled at .3115" after sitting a couple days - so a little fatter than spec. Dummy rounds made with these as cast assembled and chambered just fine in numerous .30-06's, so we opted to run them through a .312" sizer to apply the 2500+ lube and the Hornady gas checks and let the rifle do the swaging. With all the discussion of gas check separation, I'm wondering if a .310" sizing operation just to clamp the checks more tightly might be in order?

2. Any thoughts on a starting charge for H4831SC with a bog-standard .30-06 with a 1-10" twist 24" barrel? Current plan is to creep up to a point of group failure - probably with three shots of each loading on it's own aiming point. Test platform will be a CZ 550 that's been free-floated and bedded and a known shooter. Primers will likely be the military CCI 34's sunk into Lapua brass.

TurnipEaterDown

04-11-2022, 07:11 AM

I don't think sizing the base to a smaller size will crimp the check tighter. The entire lead shank will just yield more under the check. The presumption is that the (properly assembled) crimp interface is being lost by the lead bullet getting getting squeezed down in the bore to where there is no more "bite".
If I remember right, the Hornady checks are made to provide the crimp by processing them in manner that leaves the material thicker at the opening edge of the cup.
Due to the difference in elasticity (spring back), I don't think the check really is in pressurized contact at the opening of the cup after sizing either, I think the opening edge of the check is just folded into the shank, and doesn't pull off easy over the remainder of the shank that is left larger because the walls of the GC cup are slightly thinner than that opening.
It's sort of like a crimp of a revolver case into the crimp groove, but the sizing die has no roll so the thickening of the check at opening is what is making the bite and forming the crimp groove in the lead shank.
I suppose someone could make some sort of tool that would (as a secondary operation) fold the opening of the check in further, but it would be a challenge as the cups are pretty short and the tool would have to have a collapsing ring that pressed the lip in. It would perhaps look something in function like a LEE factory crimp die.

(Edited my prior comment about relative motion w/ bullet in bore, as I left out a very key word. The first 10 words now read sensibly rather than being misleading.)

Larry Gibson

04-11-2022, 10:03 AM

Larry, have you seen that kind of effect at a lower velocity and faster twist? I wonder if the twist rate has a function in the heating process, giving us the RPM limit? If PC does cause less friction then that might be a reason why the limit might be higher for PC bullets.

Yes, I have. With both the 311466 and the 310-165-FN when pressures push 40,000+ in 24" barrels of 10,12, 13 and 14" twists. The loss of the GCs was not to the extent that it was in the 16" twist 32" barrel of the 30x60 at 3000+ fps. Also, it appears the longer the barrel the more prevalent GC loss can be as there is more barrel time for the hot gasses to act on the GC and more friction. I also believe the ambient temperature has an effect on it as in 90 - 110 temperatures [I have that at early morning summer shooting times here in AZ] the barrel will never really "cool" between shots. The barrel can get very hot during a 10 shot test even with 2+ minutes between shots and air blown through the bore with a small battery pump.

M-Tecs post #63 is correct. It takes some distance, usually the 40 - 50 yards from the muzzle mentioned for the heat to penetrate and perhaps softening the lead core for the rotational forces [centrifugal force] to overcome the structural integrity of a thin bullet jacket with it spinning apart.

Larry Gibson

04-11-2022, 10:10 AM

Bigslug

"2. Any thoughts on a starting charge for H4831SC with a bog-standard .30-06 with a 1-10" twist 24" barrel? Current plan is to creep up to a point of group failure - probably with three shots of each loading on it's own aiming point. Test platform will be a CZ 550 that's been free-floated and bedded and a known shooter. Primers will likely be the military CCI 34's sunk into Lapua brass."

Suggest you start at 35 gr and use a dacron filler. "Creep up" with 1/2 gr increments.

Best to size to the throat diameter just in front of the chamber neck.

charlie b

04-11-2022, 12:09 PM

Thanks again Larry. Yeah, summers out here are brutal on barrel temps. Even when I have my shade umbrella up over the rifle it can get too hot to touch after a string. I have also thought about a fan but not gone that far yet. Guess I need to search out some battery powdered ones.

Lead and steel have very low heat conduction rates, so, seeing the effects well after the bullet leaves the barrel is not surprising. Keep in mind that supersonic air flow also imparts a bit of heat to the mix as well.

I use hornady gas checks just because of the extra crimp. Most of my bullets are seated such that the GC is below the neck of the bullet, so having one come off in the case is not something I want to experience. :)

popper

04-11-2022, 04:51 PM

It showed melted on alloy in the inside of the GC cup. Apparently, the shank alloy was melting from friction and/or the heat of gas.
Nope, PRESSURE!! Take a cast bullet, hit hard with a hammer and then pick it up - pretty HOT. About 1/50th the pressure the base of bullet sees. Simple P-V-T. Then add the friction of the GC in the barrel and you can see why GC comes off, at the muzzle. Auto oil pressure isn't very high but the oil film prevents the rod from actually contacting the metal bearing - else you get to buy a new motor.

TurnipEaterDown

04-11-2022, 09:43 PM

PV=nRT is the universal gas equation. Pressure times volume = number of moles of gas times universal gas constant times absolute temperature (if I remember the factors all appropriately).
This does not work with solids.

Metals (solids) get hot when deforming because there is work being performed on them. This is not just from pressure. Work ~ displacement & force. Translational work = force times distance. No distance no work. Deformational work is analogous. (A Joke Analogy: The fellow leaning on the shovel handle but not moving dirt puts force on the shovel, but doesn't do work...)
Place a metallic block under pressure w/o work, and there will be no heating.
Take a coat hanger and bend it back and forth until it breaks and it is hot. This is work. This also causes intermetallic dislocations in something like steels, what we call work hardening. That coat hanger where it broke will have a higher hardness number after breaking than before.

The gas pressure is actually doing little work to the bullet form, though there is some distortion both temporary and permanent. Most of the energy from the combustion process and expanding gases is being expended in accelerating the bullet, with loss to thermal transfer (to barrel & case in large extent), frictional loses to bullet on bore, and high expelled gas temperature. There is energy in that waste heat.

Oil pressure in an automotive engine (feed circuit to the rod journal) is not the pressure of the hydrodynamic wedge that separates the bearing shell from the journal. There are formulas to calculate the oil wedge pressure, and the two pressures are not comparable.

The pressure in the auto engine feed circuit must be high enough only (in the case of the rod journal) to exceed the centrifugal forces in the main bearing (fed from the outer diameter of the main commonly, it must be pumped to the center of the main and overcome centrifugal force to do that, to then be forced out to the rod by the same centrifugal forces you just fought to get to the center of the main with some assistance by residual pump pressure) and create enough flow to the rod to support the hydrodynamic wedge while flowing enough remove heat from friction internal to the viscous fluid (oil) shearing and conducted heat to the journal from rod, crank, etc.
Big main diameters need big pressure to feed rods. This is why BB Chevy's need less oil pressure to run the same RPM than would a BB Oldsmobile, Pontiac or numerous others with similar oil circuits and pressure pick up points. I have trashed the rod bearings in multiple 455 Oldsmobile engines running them to 6500 rpm, so I understand it pretty well.

This is an aside, but oils being used in machinery for lubrication, much like cutting fluids in machining processes, must carry heat away from the interface to avoid overheating of the interface. Many times, the heat it carries away is from some component conducting another source of heat to the interface. A great example of this in a piston engine is the piston pin. The piston is trying to heat that interface, and oil carries the heat away. Granted, a lot of that heat dissipation is carried by the oil flung and sprayed on the underside of the piston crown, but the point being that auto engine oils are also carriers of waste heat as well as lubricating compounds.

Bigslug

04-12-2022, 12:43 AM

So what you guys are saying is. . .

To test this high velocity cast process to it's utmost limit, we need somebody to contour a stack of 16" twist .30-06 barrels for a water-cooled M1917 Browning. Maybe it's time we apply for a scientific grant! :bigsmyl2:

All much appreciated fellas! First rounds to go downrange in about a week and a half, then probably about a month hiatus for a road trip. Back at it come June.

Larry Gibson

04-12-2022, 09:01 AM

TurnupEaterDown & Popper

"Metals (solids) get hot when deforming because there is work being performed on them. This is not just from pressure. Work ~ displacement & force. Translational work = force times distance. No distance no work."

Thanks, I had not considered the heat produced by the rapid swaging down of the bullet as it transitions from case neck to bore. Since the bullet [the 30 XCB under discussion] is swaged down from .3105 to .304 - .305 very quickly we can assume there some heat added to the bullet from that also.

dverna

04-12-2022, 05:33 PM

The heat generated from squeezing down the bullet is not going to amount to much IMO. We typically reduce a cast bullet by .002 when sizing and they do not get hot. We could determine the heat generated by reducing a bullet from .3105 to .304 by sizing the bullet rapidly in stages using three presses with sizing bushing....say from .3105 to .308 then to .306 then to .304. My gut tells me the bullets will not go up in temperature more than 50 degrees...and most of that will be from friction going through the dies.

popper

04-12-2022, 06:02 PM

I shot 165gr GC 2400 fps 308W at a yard sign. Bullet cut the 14ga steel wire in half and the recovered GC had MELTED (re-hardened but looked like soldered into the Cu) alloy in it.
The heat generated from squeezing down the bullet is not going to amount to much IMO. So FL size a 308W case and touch it - yup, quite warm. 30% of the powder energy goes into expanding the chamber and case - that is why the case gets hot!
Per the origianal question, I did chrony my 24" 1:10 ar10 carbine 165gr GC PCd 2700 fps but didn't keep any targets to show accuracy and I only shot 100 yds.
Not going to get into a discussion, PVT works for all materials. Energy does work and created heat. Yup I got a degree too.

Larry Gibson

04-12-2022, 06:57 PM

The faster the metal is worked the quicker it heats up. As was suggested, smack a cast bullet flat with a hammer, pick it up immediately and see how hot it is. then flatten the bullet in a vise the same amount and you'll find it's hardly warm. I doubt anyone here sizes a bullet anywhere near as fast as the bullet get sized going from case neck to one bearing length of travel in the bore.

charlie b

04-12-2022, 07:28 PM

PVT works for everything, in some ratio or another. PV=nRT works only for ideal gases.

There are a lot of things at work here that will heat up the bullet. Temp of gases on base of bullet, pressure on the base of bullet, friction of 'swaging' down the bullet/entering the grooves, friction of bore, friction of force imparted by the twist rate, residual heat in the barrel, heat due to compression of gases ahead of the bullet. May be a couple I have missed :)

And they all have a time/rate component.

TurnipEaterDown

04-13-2022, 01:51 PM

While I think that open source material has a large number of potential issues, here is a link that itself has internal links that might help further thought on the discussion, re: work, etc.
https://en.wikipedia.org/wiki/Deformation_(engineering)
Not meant to be a end all - definitive study, or a corrective to anyone, etc., but might help someone reading / engaged in this in some manner. More people probably read it than those commenting.

Back to the gas check retention sub-thread.
If the thought is that loosing the GC is causing the loss of accuracy (unsure that this is the thought, but it is a possibility, though loosing the GC might be just a symptom of the cause), then it occurred to me that if someone wanted to cobble up a way to to crimp a gas check more than a simple sizing die does, there Might be a relatively easy way to do it.
For a 30 caliber bullet, It seems the tools required to start with would be: (1) some sort of extended shell holder that could be bored not quite through in the center for a slip fit of the bullet and cut off the lip (rim / groove engaging portion), (2) a 7 mm something LEE factory crimp die, case necks are typically ~ 0.010" and the LEE FCD is meant to crimp the necks, (3) some 7/8-14 nuts (if I remember the common die thread right), and (4) one threaded tube w/ a flat washer welded across it (a common nut would be deep enough for what this would be for).
Attach the extended shellholder to the ram and drop the bullet in nose first. Bored hole should be deep enough to let the base stick up substantially and bullet not fall through. Run the LEE FCD in the press upside down (up from the window in the press, collet fingers toward the bullet). Use normal nut to set the position of the FCD from the top. Use another nut as a lock nut, or snug down the (non o-ringed) nut good on the press to set position an lock the die to rotation. Take the threaded tube w/ flat washer welded to it and run in down on the (now) top of the die -- turning toward body will engage the collet and create constriction at the other end.
Likely / Possibly the original top of the LEE FCD would need to be trimmed to get the bullet in far enough to get the crimp ring on the GC edge.
Hopefully the slip of the bullet in the shellholder would allow crimping the GC w/o any misalignment trying to bend the bullet. Also, the die should not turn while running the threaded tube w/ washer down to squeeze the collet into the GC, and rotation angle of the tube relative to the body would have to be controlled to get a controlled crimp. The bullet shouldn't be forced down (much?) into the shellholder as the collet is driven in to crimp, as the force to close the collet would be applied by the washer on the threaded tube not by forcing the shellholder face on ram into the collet sleeve like is designed to happen w/ the FCD. The collet would move some axially during the application of the crimp however, and I don't know how much that would be to increase the crimp a couple thousandths. I think it would be related to the angle of the collet sleeve which I don't know. Concept cobble proposal, not precision tooling.

Lots of assumptions in this cobble proposal, position of a variety of parts, does the bullet slip fit through the collet during crimping, does the collet effectively crimp the GC more or does it distort / mangle it because it isn't designed to do this, etc., but if a question is how to crimp the leading edge of the GC into the bullet shank more, this might be a way to relatively inexpensively determine if just more crimp really helps it stay on. (The opposing thought / theory is the GC gets opened & forced off by hydraulic pressure.)
If it stays on better at higher velocity, and the crimp looks reasonable, maybe an accuracy comparison could be made. Maybe it is just too much cobble and some real tooling would have to be made.

A different aspect of this discussion in general: Viscous lubricants create internal heat during shearing. Shearing happens in the fluid layer due to fluid being the interface between objects w/ relative motion (bullet & bore). Higher speed of shearing, more temperature rise, higher viscosity fluid in interface, more temperature rise.

I think that common 50-50 lube gets hot enough to vaporize at least a portion of the lube in common cast bullet loads (1200-1600 fps). At least I see a cloud at the muzzle that seems to be lube "smoke" maybe it is just finely atomized lube, I just don't know and could be wrong about supposed vaporization, but if some is being vaporized, that can't really be good for it's function as a lubricant at higher speeds than commonly used in pedestrian CB loads.

I do not know if it is practical, but lowering the viscosity of the fluid will lower the temperature rise. Maybe some different carrier could be tried w/ a lower viscosity, while being used to carry a good high pressure lubricant.
One very good high pressure lubricant is colloidal copper (copper anti-seize), but I don't know how this interacts w/ lead or how to make an effective low viscosity carrier for something like this. Maybe simple colloidal copper could be smeared on a bullet, but I really doubt that thought is too original or inspired.

Some fluids experience a greater change in viscosity relative to velocity than others. Viscoelastic fluids get "firm" if impacted quickly, and flow more easily if force is applied slowly.
Also, in general, most fluids get less viscous as temperature of the fluid goes up.
This really isn't my "bucket", but maybe someone reading this understands this viscosity/carrier part better than I and can comment on the possibility of some fluid having properties that could be exploited as a higher speed lube, or carrier for another lube, to reduce frictional heating and fluid boundary thickness/ pressure.

The fluid pressure of the lube seems to do some very undesirable things here (reducing bullet size radially), so trying to offer something on that. Even if just prompt a comment from someone who knows much more on topic.

TurnipEaterDown

04-14-2022, 12:06 AM

To anyone interested in a better understanding of metal forming, and the various effects, "Metal Forming, Mechanics and Metallurgy" 3rd edition, by William F. Hosford, in pdf form, can be downloaded online for free. A person can find this text by a search for "metal forming mechanics and metallurgy pdf"

There are sections in the text on strain rate and temperature dependence, and many others, and notably for this discussion, heating from work done on the metallic body during forming.

The equation for temperature increase during work is given in section 5.9, and it is stated to be dependent on strain in a direct manner. It uses an adiabatic assumption: no heat loss. So, this would be conservative: providing a high estimate.
Very small strains, low temperature rise.
I have not calculated the value for the lead bullet discussion here, but with small strains described, but it would appear to be low. Certainly if strains were very low (in the elastic region entirely), then the temperature rise, by work of gas pressure creating deformation of the bullet, would be low.

Most likely, at least in the case of jacketed bullets which are described by Larry as having been found on the ground hot after firing, the temperature rise is due to frictional effects, by the air as the bullet passes through, or perhaps also there is a significant contribution from friction in the barrel. I well recognize that there is significant friction effects on the bullet during barrel residence, but w/o calculating its a guess as to what matters most: frictional heating of the bullet in the air during flight, or barrel.

Again, my intention is not to "correct" anyone by providing this link to Hosford, just to provide what I believe is sound information relevant to the discussion.

Larry Gibson

04-14-2022, 09:10 AM

"Most likely, at least in the case of jacketed bullets which are described by Larry as having been found on the ground hot after firing, the temperature rise is due to frictional effects, by the air as the bullet passes through, or perhaps also there is a significant contribution from friction in the barrel."

Here's the problem I have with the theory in is the air resistance on the that is the cause of the alloy melting inside the GC. Since the air resistance is greater on the nose/ogive of the bullet the heat generated should be the greatest there, correct? Yet none of the recovered bullets which lost the GC showed any melting of the bullet nose, ogive or anywhere else EXCEPT on the shank inside the GC. Are you saying the heat generated is somehow transferred to jus the base of the bullet?

I believe it is the friction of the GC on the barrel that heats it to the point it melts a layer of alloy along the inside of the side of the GC. This allows the crimped GC to then slide off.

TurnipEaterDown

04-14-2022, 09:29 AM

Larry, Yes, my comment you returned post on was more about the bullets you stated as finding lying on the ground that were still hot (think you said something about a possible "teaching moment" for someone and fingers getting burned) and not the GC w/ lead observation you noted.

I believe that the lead on the GC you are seeing is from the combustion gas temperature of the nitro components.
I seem to remember combustion temperature of gun powders in the thousands of degrees Kelvin range. The common GC is copper alloyed, and transfers heat well. Very high temperature flame, thin conducting disk: I think you get boundary layer melting on the lead bullet base. The time exposure to the very high combustion temperatures is low, but the temperature differential across the disk is high. Very high. The energy transfer is probably significant and likely high enough to melt the lead.

Lead melts much lower than steel, and we now about flame cutting of top straps and throat erosion from high temperature gases. So, I would lean toward very plausible.
Also, consider the pictures from another earlier poster on the bullet appearance w/ & w/o the filler. Sure looked like the filler (not a good heat transfer media) cut down on bullet base localized melting / pitting.

This heat transfer isn't a difficult calculation if it's important. An assumption could be made on time exposure by simply plugging the load into GRT, getting time to pressure peak, looking up flame temperature of gunpowder in 50Ksi combustion environment, and use a simple heat transfer equation. Perfect answer: No. Good answer to determine plausible dominating contributor: Yes.

charlie b

04-14-2022, 09:56 AM

M-Tecs

04-14-2022, 05:48 PM

Hornady discovered that the standard plastic BT points were melting when the stated using a Doppler Radar chrono. The does give us some insight to point temperatures.

https://www.hornady.com/support/faqs/at-what-temperature-do-standard-tips-melt#:~:text=At%20250%20to%20350%20degrees%20%28F% 29%2C%20they%20will,100%20yards%20of%20the%20bulle t%20leaving%20the%20muzzle.

Heat Shield Technology
At what temperature do standard tips melt?
Every bullet manufacturer's tips begin to melt and deform depending on their specific material properties. In general, standard acetals and Delrins, currently used in bullet tips, begin to soften and deform at 150 to 200 degrees (F). At 250 to 350 degrees (F), they will begin to melt and badly deform. The longer the exposure to these types of temperatures, the more deformation will occur. This generally begins to occur from 50 to 100 yards of the bullet leaving the muzzle. Even though the effect is measurable with Doppler radar early in the bullet's flight, the effect on point of impact for ranges out to approximately 400 yards is small enough that it can't be exposed during shooting. Time of flight is not long enough up to 400 yards to expose the increase in drag that is measured by point of impact. Beyond 400 yards, however, the time of flight becomes long enough that the increase in the drag due to tip melting can be exposed during shooting and will result in vertically elongated groups and a lower point of impact than predicted.

https://www.hornady.com/heat-shield

https://www.hornady.com/support/faqs/why-didnt-you-put-the-heat-shield-tip-in-all-of-your-other-tipped-bullets

M-Tecs

04-14-2022, 06:24 PM

The interest here is why is the lead melting under the gas check and not on the sides of the bullet? Maybe a couple of reasons. 1) the gas check is copper and a good head conductor, which means the gas temp on the base of the bullet is 'felt' by the lead. 2) the friction of the gas check is higher than the lead portion of the bullet. 3) lube on the lead portion of the bullet is reducing further the coeff of friction of the lead portion of the bullet.

I have no idea what temperature or pressures it takes to pressure or explosion weld lead but I would suspect that is part of the equation. I've observed both processes a couple of times. In one instance it was nothing more than a copper stud being fired into a steel part to form the weld.

charlie b

04-14-2022, 08:18 PM

I used to do explosive welding at NM Tech in Socorro. The process was different based on the effect desired. I was working on a method to reline cannon barrels. Much higher pressures than in a rifle chamber. My work was a compromise to finding a slow enough explosive that would allow the welding process to take place without causing a failure in the barrel. It was a very narrow window that turned out to be not feasible for field use, ie, most of the barrels burst.

A classmate was working on cryogenic stuff and was diffusion welding, ie, polish two pieces of copper well enough and just laying one on the other will allow a weld to form over a period of time.

Time, heat, pressure.

mnewcomb59

04-14-2022, 09:43 PM

For highest pressure accuracy you want a lube groove that is closer to groove diameter. This groove will be shallow and carry less lube but it is much stronger and doesn't pump all your lube out as soon as your powder ignites. On 358 bullets I have seen the inner lube groove shank as small as .310 and as large as 350 on tumble lube designs. If you are recovering bullets undersized from lube pressure, I would try the same mold but designed with a shallower lube groove.

Also lube groove placement has an effect on how easily it deforms and pumps the lube. A deep lube groove close to the gas check on a 180 grain bullet might have 150 grains of bullet on top of it when the explosion hits it in the gas check. The same lube groove placed higher on the bullet might only have 120 grains of lead sitting above it and be more resistant to squishing out.

Heavier for caliber bullets with the same alloy, same pressure, same depth of lube groove, and same lube groove placement will obturate the lube groove easier than a light for caliber bullet at the same parameters. Heavy for caliber bullets also have a harder time biting and spinning on the initial drive band. The same alloy and same .010 drive band might be spinning 200 grains up to 130000 rpm instead of the same alloy and same .010 drive band spinning 150 grains up to 130000 rpm. For this reason lighter for caliber, lower SD bullets will be easier to push the rpm threshold.

Shorter unsupported noses will have less inertia to slump off center than a long unsupported nose.

I have seen lube groove failure where the lube groove is too weak for the desired pressure, even with hard alloy and the bullet gets undersized from the pressurized lube. I have seen PC failure like others have mentioned from extreme obturation forces. The bullet wants to grow in diameter so badly under pressure that the PC wears off the base band. Tumble lube mostly stops this unless the obturation is so extreme that the lube grooves completely collapse. The empty lube grooves on a PC bullet seam to be like a power piston shotgun wad. If you have a weak lube groove design and high pressure, your lube grooves obturate out fully and bite the rifling, then the base band resumes its extreme obturation forces and the PC grinds off the base band. If you can get a PC bullet out of the barrel without the lube grove completely obturating into the rifling, the lube groove cushions the base band obturation and they shoot clean. Once the empty lube groove obturates out all the way the base band resumes taking the brunt of the obturation force and usually ends up with that band naked with lead in the barrel.

My newest HV bullet idea is a powder coated gas check bullet with a single tumble lube groove up high on the bullet near the crimp groove. This should stop lube overpressure failure and PC obturation abrasive failure of the base band. The small quantity of tumble lube in the high placed groove might pump out around 40-50k psi compared to an equal weight bullet with low placed, deep lube groove that will pump out at 15k psi. The GC and the base driving band combined will be at least .20 before the TL groove where you usually see a .08-.10 high base driving band before the first lube groove. This long band will gently obturate outwards as one large unit, rather than a small .08 base band and low lube groove that has more bullet weight above it that wildly obturates outwards at 40-50kpsi leading to abrasive failure of PC

Larry Gibson

04-15-2022, 09:22 AM

.......I believe that the lead on the GC you are seeing is from the combustion gas temperature of the nitro components.
I seem to remember combustion temperature of gun powders in the thousands of degrees Kelvin range. The common GC is copper alloyed, and transfers heat well. Very high temperature flame, thin conducting disk: I think you get boundary layer melting on the lead bullet base. The time exposure to the very high combustion temperatures is low, but the temperature differential across the disk is high. Very high. The energy transfer is probably significant and likely high enough to melt the lead.

This heat transfer isn't a difficult calculation if it's important. An assumption could be made on time exposure by simply plugging the load into GRT, getting time to pressure peak, looking up flame temperature of gunpowder in 50Ksi combustion environment, and use a simple heat transfer equation. Perfect answer: No. Good answer to determine plausible dominating contributor: Yes.

I can give you the time to peak pressure, the Oehler M43 m3asures that if you want to calculate?

TurnipEaterDown

04-15-2022, 03:13 PM

"Charlie b" You had commented earlier on why did the lead melt at the GC interface, and not the lube interface (post #81 in thread).
Again, speculation, but I would say that there are a few things at play here on the sides of the bullet that keep this from happening: (1) the area of lube exposure to combustion products and thus peak chamber temperatures is very small, basically a funny looking keyed doughnut ring w/ ID the size of the bullet base, and OD the bore/groove, (2) lubricants have a purpose of removing heat from an interface, one way the bullet lube is doing this is to have some escaping past the bullet when it does get hot (likely primarily down the bore where the bullet has already traveled) as the bullet is shedding the lube as it goes (better be doing that, or it didn't lubricate the interface).
Since lead melts at temperatures higher than lube vaporization temp (I have thrown bullets onto my pot prior to melting and they smoke off before liquid lead fills the pot), we should have significant boundary layer vaporization if lead bullet sides were melting.
If the lube in the interface begins to vaporize due to very high temperatures in the interface we should know about that because vaporization in a fluid interface is a mechanism of cavitation, and due to cavitation very high pressure pockets would be expected to form that would pit the bullet sides and even possibly the bore.
We do not see this in my understanding of firearms shot to high round counts w/ cast bullets, so likely there is no cavitation and thus no vaporization of the lube while actually still in the bullet-bore interface. I suspect lots of lube is vaporized once it is exposed to the combustion products in the bullet's wake, and that is likely where any lube vapor I think we see in muzzle blast is formed.

The comments from "mnewcomb59" regarding bullet design for high speeds strike me as spot on, and a couple line up w/ what I was thinking a high speed cast bullet should be designed like, notably the bulk of the lube resevoir toward the front and if there were grooves toward the back they should be shallow. A couple comments he made I did not consider at all until reading his post, but again make great sense now that I have.

Larry, sure, you could give me the time to peak pressure, and they type of powder you used, and I could noodle around and make a simple engineering calculation under some assumptions.
I may not be too quick to get this done, Easter weekend and lots to do including trying to sell a restored 1969 Oldsmobile 442 that I never have time to drive, but I can look into it when I have a bit of time, for what it might be worth.

charlie b

04-15-2022, 05:41 PM

I would agree if the theories about lube behavior are correct. Same with the bullet deformation in the bore and where it occurs within the bullet. So far it is still theory with a bit of data that supports it.

Unless all PC bullets shed the drive band at the rear I really cannot agree with the theories proposed on it. Especially since some use bullets without any lube grooves at all with PC and they seem to work well.

mnewcomb59

04-15-2022, 06:42 PM

I would also like to add that some symptoms people see have counterintuitive solutions. For example, when people see leading near the muzzle only, they might think " I am running out of lube. I need a deeper lube groove to carry more lube for this length of barrel."

In reality, they are experiencing a lube groove too weak for the acceleration that they want out of the bullet. The weak lube groove collapses under pressure, pumping out the lube. The lube groove reaches peak obturation near peak pressure of the gun powder. This is usually within a few inches of the throat depending on powder charge and burn speed. Ok so now your 308 bullet is riding on a lube film at the 6 inch mark in the barrel and is swaged down by the lube pressure to .303. Once your bullet is smaller than groove diameter at the top drive band, lube presssure allows the lube to flow in front of the bullet as a plasma/vapor. If you had pressurized lube, but not over pressure lube, it would not squeeze your nose driving band under size (maybe your base band would be undersized) and your lube film would not blow past the bullet. It would remain at the lube groove and on your base band only and wipe along the bore. Now at the 15 inch mark in your .308 barrel all the lube has been pumped out of your groove along the barrel behind the bullet and in front of the bullet because of your undersized nose drive band and your .303 bullet is now naked. There might be residual pressure and your bullet bumps back up to .308 but by the 20" mark it leaves a lead wash because it has been riding dry.

You might see lead wash or leading in the last two inches of your barrel and think "Hmm it ran out of lube. I need the same bullet but with the lube groove cut deeper." Now your new mold arrives and you get leading even earlier in the barrel because the new bullet with the weaker lube groove pumps its lube sooner, makes the bullet more undersized than before as it rides on its lube gasket, and runs out of lube earlier in the bore.

In reality if you are seeing a lack of lube star or lead wash or leading in the last few inches of the barrel you need a shallower lube groove or keep the same lube groove and move it further towards the nose of the bullet because it will pump its lube out slower at any given pressure.

dverna

04-15-2022, 07:39 PM

Larry, or any one, does a jacketed or PC bullet lose .005 in diameter as it travels down the barrel, or is this only a phenomenon with lubed bullets?

mnewcomb59

04-15-2022, 08:27 PM

It is only a phenomenon with lubed bullets with a full lube groove. And only when those bullets are pushed at a pressure too high for a given lube groove design. There is a given pressure where everything works as intended, where the lube makes a gasket that rides with the bullet. Raise the pressure by 5k psi and all of a sudden the lube groove is pumping too hard, squeezing lube out along the front and back of the bullet and making the bullet undersized.

charlie b

04-15-2022, 08:29 PM

Bigslug

04-15-2022, 11:30 PM

I agree.

Yes, there are a lot of factors that contribute to the heat gain, but, most are not as significant as the friction factor or the gas temp on the base of the bullet. Things like the compression of air in the bore and the air friction outside the bore would serve to keep the bullet hot after it left the barrel, maybe even increase the temp slightly.

The interest here is why is the lead melting under the gas check and not on the sides of the bullet? Maybe a couple of reasons. 1) the gas check is copper and a good head conductor, which means the gas temp on the base of the bullet is 'felt' by the lead. 2) the friction of the gas check is higher than the lead portion of the bullet. 3) lube on the lead portion of the bullet is reducing further the coeff of friction of the lead portion of the bullet.

Another data point. I have found when sizing bullets that the GC has a slightly larger dia (~0.0005) than the body of the bullet. The simple explanation is the copper GC has a 'spring back' and the lead has less. Higher yield limit maybe the source? Is this related to how the GC acts in the barrel or why it is heated more?

An excellent post that's sparked a couple of brain waves - maybe useful; maybe not.

As to the forces exerted upon the gas check at the base of the bullet. . . My thoughts turned immediately to my Dad's various black powder toys that use an assortment of base wads behind the bullet. These have been dry cardboard, poly-waxed juice box, poly, felt, lube-impregnated felt, and just straight lube discs. Obviously, this sort of thing is more easily applied to straight-wall cases than bottlenecks, but it seems that these kinds of things could serve to function as an ablative / consumable shield to the base of our gas-checked bullets. They would absorb the hurtin' generated by the gas buildup while pushing the bullet, without being a part of the bullet. For the application of a bottlenecked round, something easily stuffed on top of our charge (like Dacron) chosen for its ability to seal, buffer, then separate might have some benefit. To what degree Dacron serves these ends beyond being just a filler is a question for the more experienced Peanut Gallery

Regarding the gas checks having more springback and their diameter being greater than the bullet they're sized onto. . .

* This first got me thinking about the copper jacket fouling we see in everything from hunting rifles down to 9mm pistols. The common theme seems to be that good polished "match" barrels seem to do this less, but I'm wondering if this is due to friction against rougher surfaces as is commonly thought (at least by me anyway), or if the same forces of gas blow-by and vaporization that we see with poor sealing of lead bullets are contributing to copper deposits.

**This also got me thinking about how the early cupro-nickel jackets were known for fouling very badly. Was this due to less resistance to friction, or not sealing as well? Point: are our current copper jackets and gas checks just a step to some better material?

***As mentioned, lead rapidly compressed will get hot. That heat will bleed into the conductive gas check. . .and maybe even concentrate there??? The check is getting the double-whammy from behind by the powder charge. That copper is conductive, doesn't have a lot of mass, and if the lube boundary and gas pressure are indeed negating each other at the base of the bullet, the heat getting dumped into it has nowhere to go but the vulnerable lead bullet base.

The air quality here is horrid right now and my eyeballs and sinuses hate me tonight - - so my fuzzy brain is only seeing these dots (spots? :veryconfu) and not connecting them very well. I am however thinking the base wad / filler concept would at least limit the sources of heat the gas check takes to those forces coming from the front (compressing bullet).

Larry Gibson

04-16-2022, 09:29 AM

Larry, or any one, does a jacketed or PC bullet lose .005 in diameter as it travels down the barrel, or is this only a phenomenon with lubed bullets?

Jacketed bullets do not. The ones I've recovered that were measurable were at groove diameter if the bullet was very close to groove diameter to begin with. If shooting a slightly undersized jacketed bullet then they would be at groove diameter IF the load was sufficient enough to obturate the bullet. For example a lot of, if not most thick or soft steel jacketed bullets won't obturate to seal the bore. They come out as the went in.

I've only recovered 2 PC coated bullets that were not lubed. They were 30 calibers shot out of my Palma 14" twist rifle with a .3085 groove dimeter barrel. The muzzle velocity was 2550 fps. The bullets went in sized .311 and came out, as best as I could measure, very close to that. Since PC'd bullets do not ride a layer of lube in the barrel (unless they also have been lubed) it is my thinking that is the reason the RPM Threshold for a given cast bullet will be higher than if the bullet is conventionally lubed.

Larry Gibson

04-16-2022, 09:50 AM

If someone could tell me how to capture bullets without deforming them (other than a big snow bank :) ) I would do it. I will be shooting some into a sand bank tomorrow. Will try to dig some out and look at the bases and under the GC's.

I save up newspapers until I have a bundle that is 30 - 36" thick. I place/line a cardboard box big enough and sturdy enough to hold the bundle while allowing for expansion with a sturdy large garbage bag. I've found the thicker large garbage bags to be best. I then fill the lined box with the papers in it and let soak 48 - 72 hours. As the paper soaks up the water more water is added until the newspapers are sopping wet and won't soak up any more water. I usually have the box sitting on a piece of 3/4" plywood (just a bit larger than the bottom of the box) already in the back of the PU. That way I and a partner don't have to initially load it as it will be very heavy. At the range the box on the plywood is set on the ground with one face toward the shooting position. With full power loads and WQ'd bullets I set the bundle at a range where the velocity will be about 1500 fps +/-. If testing for expansion I set the bundle at the intended test range.

I can usually get 8 - 10 shots into the bundle. then when locating the bullets you can peal the papers back front to rear following the "wound channel" to the bullet looking for the GC and observing/comparing the size of the wound channels to the recovered bullet. I usually slit the box/bag along the 4 corners and lay the sides out when doing this. When done smaller sections of wet still heavy newsprint are easily put into another bag in the back of the PU for transport to a recycle dumpster.

It's a pain which is why I don't do it all that often and then only when I really want to know.

dverna

04-16-2022, 09:52 AM

Thanks for the reply Larry. It was what I expected but good to have it confirmed.

It makes me wonder how much rifling engagement is lost with a lubed bullet at high velocity. Are the rifling marks imprinted in the first few inches of barrel travel before the lube has had a chance to squeeze the lead bullet down?

I know liquids are not compressible, so as the lube melts it needs to fill that space between the barrel and the bullet or gas will blow by. It would seem more lube is better to insure that happens, but I know that flys against the experience that too much lube is normally not good.

I am having problems understanding the mechanics of what is happening. Knowing the bullet is sized down as much as Larry has shown is an important factor to understand....and I cannot get there.

BTW great thread and this is how we learn. As most of you know, I am a jacketed bullet guy when it comes to HV rifles but I still find this very interesting.

mnewcomb59

04-16-2022, 10:04 AM

It makes me wonder how much rifling engagement is lost with a lubed bullet at high velocity. Are the rifling marks imprinted in the first few inches of barrel travel before the lube has had a chance to squeeze the lead bullet down?

It depends on the cartridge. Most handgun cartridges reach peak pressure in the chamber or cylinder. They are likely pumping some lube already as they engage the throat. Some overbore rifle cartridges with lots of slow powder reach peak pressure at 12" down the barrel. The area under the curve on graph of pressure vs time is acceleration. Peak acceleration occurs at peak chamber pressure. We say lube groove obturation is a function of pressure, which it kind of is, but it is really a derivative of pressure over time a.k.a acceleration. If two bullets leave the muzzle at 2600 fps, but one used 45 grains of fast powder and the other used 55 grains of slow powder, the slow powder has more gently accelerated the bullet so the bullet pumped its lube slower and reached peak lube groove deformation later in the barrel than the fast powder. Since both bullets reached the same velocity we can be absolutely sure that they received the same total amount of acceleration and therefore the same amount of lube groove deformation. Even though one bullet experienced less peak pressure, the area of below the curve on both bullets pressure graphs is the same.

charlie b

04-16-2022, 03:42 PM

The current theory of copper fouling as I understand it is the gases of combustion form a plasma with the copper and that is deposited in the barrel. The rougher the barrel, the more blow by and more copper deposited. Undersized copper bullets will severely foul due to the excess blow by. Which is also why match/hand lapped/ barrels exhibit little to no copper fouling?

Plain based lead bullets would follow that same rule, IF, they are not 'bumped up' to fill the throat and grooves on firing. Again, my understanding of current theory is this is the primary cause of lead fouling in firearms, ie, the bullet not filling the throat/grooves. Gas checks are an added factor and I really don't know how they work so well. I've had gas checked lead bullets 'clean' the copper fouling from a barrel. Maybe the pressure on the base forces the edges of the GC outward? Maybe this force comes from the upset of the lead bullet around the base? Does this function act that much better than a copper jacketed bullet that 'probably' has no upset to force the copper against the grooves?

My experience with the few 'undisturbed' copper bullets I have recovered is the same as Larry's, no change in dia from the bore.

I have to admit I failed at the range today. Fired 45 XCB's at 2200and 2400fps and didn't find any of them in the backstop. Normally I just dig back about 12" and they will all be in a 'tunnel' of less compact dirt/sand, fairly easy to find. Today, nothing. I'll just hang my head here and will try again next time.

Larry, father-in-law and I used to do the wet paper thing when testing expansion of lead bullets. We only did a few rifle bullets back then so don't remember if the bases got upset terribly or not. Lots of fun trying to find bullets in that stuff :) We ended up using the small moving boxes so we could at least tell which box the bullets were in. I can't handle that much weight these days, and, I'd like a non-destructive recovery if I could. One reason is I want to see what the bore riding noses look like.

The good news is the 2200fps powder coated XCB's out of a 1/10 twist barrel grouped less than 3" at 200yd. :)

I will try them again next outing.

charlie b

04-16-2022, 03:59 PM

PS I suspect the PC acts quite a bit differently than the lube. Like discussed, the lube forms a layer around the bullet, distorting the bullet as it does so. The PC is already in place so the 'lube layer' of PC doesn't change during firing.

Need more data!! Motto of the test engineer :)

Bigslug

04-20-2022, 09:38 PM

Some good early preliminary results. . .

My Retired Old Man Of Leisure got out to the 100 yard line to zero a new peep on his recently-acquired '95 Winchester in .30-40 Krag, and he loaded up some cast-long-ago .30 XCB's cast of air cooled WW+2%, as well as some 2/1 Lino/#2 Accurate 31-170EN's (his design that has been showing promise for an HV .30-30 practice bullet) - - both with H4895.

Seems like a pretty good test bed for a lot of this: the .30-40 has a hella-long neck for packing on the series of skinny lube grooves; the rifle has a 28" barrel which is close to Larry's operational concept; and it's rocking a 1-10" twist.

The 13BHN XCB's are undoubtedly a little too soft for this kind of thing, but they still grouped 8" high x 3" wide in a workup string in not great conditions with a number of variables still to sort out (new sight, unfired brass, and awaiting a replacement sprue plate for cleaner cuts). 37.4 to 37.6 grains seems to throw it at 2525 fps

The harder 31-170EN's workup dropped 8 out of 10 into a 3" circle with some weird velocity fluctuations in the 36.5 to 38 grain charge range, but 2500 seems to be very do-able here. He's already got a tweaked-for-the-Krag version of this mold on order.

Clean barrel for both bullets with 2500+ lube spooge at the muzzle. We seem to be off and running!

Friday, we test the XCB's with the hard alloy and 4831SC in the .30-06. Bullets hand sorted for the cleanest sprue cuts from the warped plate. Stay tuned!

Bigslug

04-23-2022, 07:27 PM

So, baby steps.

Got the 24", 1-10", CZ .30-06 to the range yesterday for my first .30XCB experiment using H4831SC and 2500+ lube. Bullet alloy was 1 part Lyman #2 to 2 parts linotype at about 19BHN. Lapua brass. Primers were Federal Gold Medals. Empty space in the case loosely filled with Dacron.

Starting charge was 38 grains and worked up in steps of half a grain. Three shots fired for group at each step over an Oehler 35P. Nine shots fired, then the barrel was allowed to cool back down to "room temperature" (a fairly cool, windy day in the '60's).

For the less intense 38 to 46.5 grain charges, we used our "2nd quality" bullets with the lumpier sprue cuts. These took us from a 3-shot average of 1754 up to 2222fps. Worth noting is that combustion of the propellant was not really complete until we reached 43 grains. Prior to that, there was a significant trail of unburned granules left at the 6:00 position of the bore. None of these loads had trouble staying in the 6" 9-ring diameter of an SR-1 target and we had numerous instances of two in one hole, and plenty that would hold the 3" 10-ring.

We hit the pretty-based "1st Quality" bullets at 47 grains. Best group for the day was about 1.5" inches at 2267 fps with the 47.5 grain charge.

The wheels started to come off the wagon shortly thereafter. 50 grains took us to 2374 fps and it was decided that accuracy had left the building. At 51 grains and 2415 fps, we experienced the first bullet completely off the 10" SR-1 repair center. 52 grains got to 2481 fps, were spread out at over a foot. Metal fouling was beginning to appear on the crown over the last several groups. There was an impact mark from a gas check on one of the chronograph's sky screens, so definitely experiencing some of the previously-discussed integrity issues

We were intrigued enough by the lower speed accuracy and the earlier results from Dad's '95/Krag to heat treat and water quench some of the older WW+2% versions of the bullet. Going to run these from about 46 to hopefully 58 grains to see what transpires. Next range adventure hopefully in a few days.

popper

04-25-2022, 03:20 PM

same total amount of acceleration - but that is not what counts except for muzzle fps. F=m*A and F comes from psi and base area (dia) of bullet. So, A is proportional to psi curve. A= (psi*pi *r*r)/m.
Metal fouling ... beginning to appear on the crown. Definite leading! I get some in the BO linear comp. Lead scraping by the GC and HV 'dust' exit from muzzle (calculated muzzle gas exit fps is 10-20% greater than the bullet fps -bernouli effect)? I only recovered one GC and it was dished so I assume, as the edges are stiffer than the center, the edges get twercked outward adding to the scraping effect. And possibly loosening the GC.
My rifle moulds are effectively smooth sided, just a small groove for collecting displace alloy and about half way in the drive band (drive band is approx 1/2 - 3/4 of bullet length). They shoot fast and well. I did put one coat of BLL on some, no difference I could tell. I have some only BLL'd to compare in 308W yet. Shot 2 coats BLL in BO GCd and results were good, compared to PC, both in 18-1900 fps range. 2400 may be different. BLL doesn't get pumped from a groove but may also have a layer effect.

mnewcomb59

04-25-2022, 06:00 PM

same total amount of acceleration - but that is not what counts except for muzzle fps. F=m*A and F comes from psi and base area (dia) of bullet. So, A is proportional to psi curve. A= (psi*pi *r*r)/m.

Acceleration is the derivative of the psi curve. The rate of acceleration is greatest at peak chamber pressure. There might be some slow rate of acceleration that is too slow to pump a given lube groove, but it is likely at points in the graph below 5-15k psi depending on lube groove design. Outside of these low pressure times and locations on the graph, if you add up all the time under the curve it will give you a total amount of lube groove pumping acceleration in a load.

On two loads that both reach a given velocity but with different peak pressures, they will have the same amount of total acceleration above the cutoff PSI (where psi is too low to pump the lube groove) and therefore the same amount of lube groove deformation. The difference is that the lower pressure load pumps its lube out slow and steady as it travels down the barrel and the high pressure load pumps the lube harder and sooner and pressurizes the lube too much, squirting it past the nose of the bullet early in the barrel and making the bullet undersized as it rides on its lube gasket. Then the bullet runs out of lube too soon in the barrel because it was flowing in front of the bullet instead of wiping on the barrel as the bullet goes past.

Have you ever recovered any of your small displacement groove bullets after firing? I bet the groove gets deformed at least 50% meaning at least some of the tumble lube in there would be pumped out. I have only been experimenting with TL and PC because I have some mold designs with weak lube grooves and small base bands that like to scrub the PC off the base band with high pressure loads. We have seen time and time again that only the tiniest amount of lube is needed if you are using anything modern other than mutton tallow and frog skins. If your small groove is placed to where it moderately deforms at the pressure you commonly shoot, it will probably shoot great and give your PC a free ride for at least the first half of the barrel, leaving it in better condition at the crown leading to less PC fouling in the comp. The small amount of lube fouling will be easier to clean than baked on vaporized PC.

popper

04-26-2022, 10:46 AM

Have you ever recovered any of your small displacement groove bullets after firing?
Nope. They are PC'd and the groove is there to collect alloy from barrel sizing and lands. I load near max in the rifles, have a PB of similar design I've pushed to 2k fps in 300 BO, MOA at 100. Objective was to eliminate the 'tail' at the base from all the moved alloy. Seems to work fine.
Yea, I tried to give a simplified version of the equation.
It's interesting if you play with GRT or QL, slow powder doesn't (normally) completely burn but fps increase is very low toward the muzzle. Wasted powder but it won't burn right if you 'short it' of powder, pressure isn't high enough for good burn. One 'solution' is a heavy for cal. bullet (momentum) to get burn eff. up and hard crimp.
easier to clean than baked on vaporized PC - PC isn't baked on, dissolves with solvent, the hardened lead/powder residue is tougher.
I have recovered some 40sw and the normal lube groove on them didn't appear to be collapsed much. They were coated, not lubed. Did have some base 'tail'. They were shot into a rock pile, 98% retained weight and the coating was pretty much removed from the sides AND nose (TC design)! Nose was close to body dia. so assume the coating there fractured from impact. Coating left on the body had turned white - coating was green.

Larry Gibson

04-26-2022, 12:57 PM

Here's 5 recovered XCBs from soppy wet newsprint at 300 yards. Velocity from the 30x60 XCB was 2900 fps at muzzle. The bottom bullet is an as cast 30 XCB with just the GC crimped on. The 30 XCBs are sized. ,310 before loading. Note little if any collapse of the lube grooves on any of the recovered bullets as compared to the "as cast" XCB. No gas cutting is seen on any of the 5 bullets. The two recovered GCs show no alloy melting given 2900 fps at 50,000 psi.

The recovered diameter of each bullet;

A. .3061
B. .3063
C. .3062
D. .3065
E. .3065

The unfired "as cast" XCB is .311

299527

With a properly designed bullet for the task such as the 30 XCB cast of a proper alloy we see how well the bullet holds up to the higher pressure (50,000 psi) needed for the velocity.

Bigslug

04-27-2022, 01:06 AM

Pop & I did a rocket run to the range yesterday afternoon after I got off work to get a last bit of "SCIENCE!" in before a forced 3-week break (vacation). Gonna need to look hard at the chrono data, but for water quenched WW+2% out of a 1-10" twist, Chuck Yeager's "demon" seems to be living around 2,300 fps and 53 (ish) grains of H4831SC.

The encouraging bit in there was we did an abbreviated ladder workup string of six rounds across three grains of powder all went into about 3 MOA, so at least once we figure out where the failure point is, there's plenty of space to work further down.

Getting the lead vapor deposits at the crown despite the 2500+ and a nose-dip of BLL, but in spite of that, the bore itself seems to be running very clean.

charlie b

04-27-2022, 09:18 PM

Larry, have you ever seen anything written about bullets being smaller due to the lube layer? I have not. Have you discovered something no one knew about?

Just curious, can you measure the dia of the bullets in the nose section, as far forward as you can and just in front of first lube groove?

PS did you have to remove those GCs from the bullets or did they separate after entering the bullet stop?

Sorry, last one. What dia are the GCs on the bullets?

Bigslug

06-19-2022, 10:52 AM

More theory on gas check separation:

Both copper and lead are getting squeezed equally by barrel and our mysterious "lube force", and there is the possibility of bullet bases getting melted under the gas check.

Springback is going to be greater on copper than lead, and its affect is most likely to be seen at the front edge of the gas check. If its grip on the bullet has been compromised by compression and liquefaction at the rearmost corner, that front edge is our last remaining point of contact, and now it's gone.

So on the one hand, I'm now thinking that annealing gas checks to render them as dead soft as possible may be a key part to this. On the other hand, I wonder if, due to the pressures and heat involved at these high speeds, if the gas checks are getting flash-annealed in the bore and this theory is much ado about nothing.

Larry Gibson

06-19-2022, 12:22 PM

charlie b

Apologies for the late response, just saw the post.

Larry, have you ever seen anything written about bullets being smaller due to the lube layer? I have not. Have you discovered something no one knew about?

I take no credit for the "discovery" as such. Perhaps I've just brought it to the forefront is all. In years past I've read several queries from those who have recovered cast bullets and found the diameter was less than the barrel groove diameter. There were many different suppositions as to why but the one that seem most logical was the bullet had to be riding on a layer of lube. The lube, not being compressed, added to the swaging effect on the bullets diameter on muzzle exit. Further testing of various cartridges at low medium and high velocities by myself,goodsteel and Lars45 have verified this.

Just curious, can you measure the dia of the bullets in the nose section, as far forward as you can and just in front of first lube groove?

The diameters of the noses are, where not obviously bulled by impact, is the same as the drive bands.

PS did you have to remove those GCs from the bullets or did they separate after entering the bullet stop?

No, I did not remove those 2 GCs. They were recovered in the test media about 1/3 to 1/2 the penetration distance.

Sorry, last one. What dia are the GCs on the bullets?

The diameter of the 2 GCs still on the bullets is the same as the drive bands. They are still tight with no indication of "springback".

Larry Gibson

06-19-2022, 12:23 PM

Tripplebeards

06-19-2022, 07:29 PM

My avatar was 2100 fps out of my 1970 Marlin 336 chambered in 35 Rem. I shot a group at 200 yards right after the avatar group that measured 2 1/4”. Used smokes PC, a hornady GC, and sized about .0025” over. Alloy is 50/50 COWW and pure with 2% pewter added to total. The boolit is a group buy 200 grain HP. I also had a Ruger American 450 bushmaster I pushed all the way up to 460 S&W velocities but found out the best accuracy came around 2250 fps. It grouped 1 1/4” with 100% COWW alloy the was PCd,GCd, and sized a thousands over. I shot a 1 1/8th group with the same alloy and boolit set up but not water quenched. Boolit was a lee 300 grain FN. I do weigh my boolits and separate within 1 grain increments which imo everything helps when squeezing the tightest groups. They have been the only two rifles I’ve tried cast boolits in to date…so far.

charlie b

06-19-2022, 08:12 PM

Thanks Larry. Good info.

450 Fuller

09-01-2022, 11:17 AM

"Gas check separation..." Even more critical in bottle-neck cases. BTW-If the GC falls off, separates and falls off
into the powder column during the seating operation or before, you will encounter a serious/dangerous pressure excursion.
A loose GC moving toward the neck in front of ignited powder IS NOT your friend. (Seen and witnessed.)
For me and my house: straight wall cases IF a GC is used. The possible exception is the 30-40 Krag case.
A very long neck that that would allow seating a GC d cast bullet to a chamber with a long leade/free bore. GCs are rattlesnakes sitting under a rock:
they might stay and not bite...but.

My use of cast boolits is somewhat limited to the following cartridges and rifles:
Original 1885 Winchester HW Single Shot chambered in 45 2.1 inch; Sharps 1874 chambered in 45/2.1;
Winchester pre-war Model 71 in 450 Alaskan; Model 71 Deluxe pre-war in 450 Fuller.

" Only the dead have seen the end of war" Plato

"Tolerance and apathy are the signs of a declining society" Aristotle

Isaiah 53 Mathew-John

Khe Sanh-5th SF Group (ABN) MACVSOG-(1971-72) NRA-LIFE

charlie b

09-01-2022, 07:41 PM

YMMV. I've fired a few thousand rounds through my .308 now. All but a couple hundred have had gas checks seated below the neck and none have shed a check in the barrel. I've only recovered a couple hundred and all still had the GC's on them after penetrating around 12" through a dirt/sand backstop.

I use only Hornady gas checks that crimp securely onto the base of the bullet. Most of the time I powder coat after applying the GC's.

charlie b

11-12-2022, 08:47 PM

So, after looking at this kind of thing for a while I decided to try a few things. First, in a discussion with Mr Gibson about ideal cast bullet barrels he brought up the slower powder again. I used to use Varget for cast loads but at lower levels, frankly where Varget does not do well (it likes high load densities). I've been using a lot of 4198 and 3031 instead and investigated higher velocity accuracy with those. I hit 'the limit' at around 2200fps. It occurred to me after all this that the faster powder was a contributor. I had some 4166 and it has done OK at sub-2000fps loads. Since it was slower I decided to ramp things up a bit.

Rifle is a Savage Axis. Barrel is a .308Win from a Savage 12BVSS (26" stainless, 1:10 twist, fluted heavy varmint contour) and it has a bit over 4000 rounds through it so far, about 3000 of those have been cast. At sub-2000fps it is consistently under 1 1/2MOA. Most of the time (including this time) I am shooting the Accurate 31-210E bullet.
They are nose and body sized, powder coated, then nose and body sized again (.302 nose, .310 body).
They are sorted into 0.1gn batches. Hornady gas checks. Due to the throat they are seated fairly deep. The gas check is below the base of the neck.

306807

For this series I loaded up at my 'standard' 30gn of 4166 to give me right at 1970fps. This was my 'control' load. I then loaded up 36, 38 and 40gn. Keep in mind the max load for 4166 with a 210gn bullet is just over 40gn at just over 2400fps.

So, on to the shooting. Early morning, temp in the 40-50F range. Wind was gusty at 5mph from left to right.
I shot the control group at 200yd to foul the barrel and confirm the zero. I adjusted for wind and went to 500yd.

306809

My main target was a 5" square gong. Yes, that is ~1MOA at 500yd. But, with a camera I can see the dirt kick up when I miss. I shot the rest and had some interesting results so I made up a video. I clipped out everything except the shots and only put in the 38 and 40gn series.

Bottom line was, the 38gn load avg was 2340fps and had nice tight group. The 40gn load avg was 2455fps and definitely showed the effect of exceeding the RPM limit. Note that the extreme spread for the 40gn load was only 10fps!!! The es of the 38gn load was 40fps, and it still was pretty decent on target. The 40gn load was definitely max or over for this rifle with the cases having 'sticky' extraction.

I think I can see a cone shaped 'wobble' from some of the bullets at the higher vel. I was kind surprised how close the first two came to the target.

https://www.youtube.com/watch?v=cHZxFLsDLlE&t

PS forgot. Of the two higher vel bullets that actually hit the target board, the holes were perfectly round. So the bullets did not hit grossly yawed or sideways.

Larry Gibson

11-13-2022, 09:32 PM

Very interesting aand excellent examples. If you look at the video carefully you can see the helical arc of the bullets flight.

charlie b

11-18-2022, 10:30 AM

Thanks Larry.

The 'good news' is I am at least 300fps faster than I thought I could go with this setup and maintain decent accuracy. Being at jacketed velocity for this weight bullet is a bonus. Now I hope I can repeat it.

I did pick up some N150 powder to try out. It is a little slower than 4166 so will see if I can eek out a little more velocity with it. Will also have to make up some XCB loads at same velocities and see what happens.

Alferd Packer

11-19-2022, 11:32 AM

All good info!
I love this thread!

popper

11-19-2022, 12:45 PM

two pieces of copper well enough and just laying one on the other will allow a weld to form over a period of time.
NASA found a problem with connectors in space - they weld together!
Getting old so I don't chase HV anymore. Results of my tests are - keep groove shallow - weakest point to twist. Bullet must be a high quality one. Alloy needs to be tough, I add a tad of Cu and NO tin. I did push a 145gr coated PB to 2050 fps (chronyd) from 1:10 18" McGowan barreled 300 BO AR, hot load of H110. Got near MOA @ 100 as sprue cut kept base from being completely flat. Had to really bang the plate to get the cut. IIRC had an almost 10 shot circle on the target.

charlie b

11-19-2022, 01:59 PM

Thanks.

It's called diffusion welding. The 'smoother' the surface the better the joint. The use I know of was in low temp physics work where any welding 'filler' was a contaminant.

I am still surprised I got over 2300fps with some accuracy. If I can repeat it I will consider it a success.

So, the other message might be that if 2350fps is 'ok' with a 1:10 twist, then a 1:12 twist might be good for 2800fps?

waco

11-19-2022, 02:42 PM

This was a few years ago. Rem 700 .308 1:10 twist 30xcb at 2600fps, sub 2moa at 500 yards.
Nice job on the results you are getting!
https://www.youtube.com/watch?v=l9VDouNYi7A&t=2s

popper

11-19-2022, 07:32 PM

I'll elaborate a bit on bases. I see vids of guys hammering the plate to cut the sprue. Looks good right? One end is free and the other is under bevil washer tension. Base sprue hole is small but is cut at an angle and is very difficult to measure. It is very difficult to get a good square cut! PB or GCd, same.
Flatness of the plate and squareness to centerline is another problem area. Right, it could be a small angle but at 45-50K psi, the radial component of force on the base could be 5k psi, pushing the base sidewise in the neck. GC fix it? Nope, just seats flat to the base - we hope. High quality moulds help a lot.
Yrs ago I nicked the base of 40sw and got a nice 3" circle @ 7 yds on target. Otherwise an accurate bullet.

charlie b

11-19-2022, 08:34 PM

This was a few years ago. Rem 700 .308 1:10 twist 30xcb at 2600fps, sub 2moa at 500 yards.
Nice job on the results you are getting!
https://www.youtube.com/watch?v=l9VDouNYi7A&t=2s

Thanks.

Yep, I followed your video when you first posted it as well as the other thread that is locked now.

My quest goes on, <MOA or bust! :)

centershot

11-20-2022, 07:30 AM

missionary5155

11-20-2022, 07:55 AM

Always remembering fit of cast projectile to the throat / lead is principle.
But your sure moving that chunk of lead along in good form.

Larry Gibson

11-20-2022, 12:14 PM

The use of a properly designed cast bullet, such as the 30 XCB, for higher velocity shooting is one of the ways to push the RPM threshold up. The same with adding copper making the alloy a quadra-alloy instead of a ternary alloy. As does adding a "jacket" of PC, paper or copper/brass.

Charlie b is certainly pushing the Threshold up with the techniques he is using. He is doing well in his quest for MOA accuracy at HV.

charlie b

11-20-2022, 05:31 PM

The difference with mine is the LARGE bore riding portion of the bullet. I keep threatening to make up a large catch box so I can recover some bullets without distorting the noses just to see how much they engrave in the bore or if they upset to fill the grooves.

I do not take a lot of care with the sprues. I do know that they are mostly flat, but, I don't inspect them that closely. I do make sure to put the GC's on square to the bullet and inspect to see that they are. At one time I used a dial indicator, but, it showed so little variation I quit that one.

I have two theories there. 1) the chamber pressure is enough to drive the GC onto the base and 'flatten' any irregularities. 2) the pressure really does nothing to move the GC during the trip through the bore so it stays where it was seated. Don't know which and don't really know how to check. I've measure the grease groove above the GC before and after firing and find no differences. Don't know if that means anything or not, except maybe the few bullets I have recovered were ones with 'flat' bases before seating the GC?

A lot of these questions we are asking could easily be solved if we could gather the correct data. It may also tempt me to do some 'test engineer' stuff. I used to get paid a lot of money for doing that kind of stuff, so will see what I can do without deep corporate pockets :)

charlie b

11-20-2022, 05:41 PM

Always remembering fit of cast projectile to the throat / lead is principle.
But your sure moving that chunk of lead along in good form.

Very true. The bore riders I use are an interference fit in the bore. I also try to set the bullets such that the first drive band is slightly engraved into the rifling. If I decide to unload a cartridge I have to 'tap' the bolt handle to get the bullet out of the bore. And, yes, sometimes the bullet stays in the bore and has to be tapped out with a range rod.

So, there are two 'reference points' on the bullets. The lands touching the nose section and the drive band engaging the tapered portion of the throat.

I also check runout on the loaded cartridge to make sure the bullet is not angled in the case. I ended up modifying a Lee seating die to make that a non-issue anymore. The Lee die had just a bit too much 'slop' on the sliding section of the die so I shimmed it to be a closer fit.

405grain

11-20-2022, 06:14 PM

This is an excellent thread, with a treasure trove of information. My skill sets haven't progressed to the point where I'm ready to extend my cast bullet ranges out the point where I'd need high velocity, but much of the information that has been presented will certainly benefit accuracy improvement at regular velocities. Some of the recent posts have mentioned how cutting the sprue can leave a bullet with a less than perfect bullet base. When I read this I had a thought. When reforming brass to convert one caliber to another, they make a thing called a "cut-off die". This is a reforming die that's made from hardened steel, so that the brass that protrudes from the top of it can be cut off with a hacksaw. Why don't they make something like this for cast bullets?

What I'm visualizing could be made from a pair of blocks of heat treatable steel and a drill press: Make up a pair of blocks that have alignment pins and faces that match together, not too different from a set of bullet molds, but don't need slots for mold handles. Machine a hole into the center of this block set, again - similar to a bullet mold. There doesn't need to be any features in this hole, ie: driving bands, lube grooves, ojive, etc. You don't need any of these, it's just a smooth hole. The inside diameter of the hole is the same as the outside diameter of your bullet. I'm going to call this a "guide hole". When you place a cast bullet nose down in the hole in these blocks the base of the bullet will be flush (actually slightly above flush) with the tops of the blocks. You can even have a threaded hole under the guide hole, or shims, or something, so that you can use a set screw to adjust the height of the bullet when it's held in the blocks. Now heat treat the blocks so that they're good and hard.

The way I envision this working is that you close the hardened blocks with a cast bullet inside. The blocks hold the bullet in place. The bullet base is ever so slightly above the level of the tops of the blocks. With one or two swipes of a sharp file you will have a flat & perfect bullet base. If you want to go crazy you could even make up a set of blocks with multiple holes. Will it work? Who knows!? To the best of my knowledge it hasn't been tried yet, but on paper it sounds like something worth trying.

Digital Dan

11-20-2022, 06:28 PM

This discussion makes me smile a bit. I’ve learned how to make lead do what’s needed for my purposes, some of it on this forum. Fastest I’ve used are in the .30-30 in the neighborhood of 2200 FPS. Another thing learned before I started casting was the art of paper patching. 300 gr of pure lead properly patched is good for 8 shots sub MOA at 100 with max loads in a .44 mag., velocity ~1600 FPS. It is also quite the hammer on hogs and deer.

Should I ever feel compelled to go fast with lead it will be a bit harder than pure, and paper patched.

charlie b

11-20-2022, 10:15 PM

Some of the accuracy 'nuts' in the past developed nose pour molds for the reasons we are discussing. I think Pope used some in his accuracy testing. Eagan was also one of those. The bullet I use is a copy of one of his designs, originally in a nose pour mold but mine is a conventional design mold from Accurate.

Yes, there are all kinds of dies you can make to 'fix' issues with cast bullets. I know at least one person who made a special die for seating gas checks. As above, a bored hold to precisely fit the bullet and a slightly rebated section where the gas check was placed. An arbor was used with a 'standard' nose punch to seat the bullet squarely in the gas check.

FWIW, I paper patch bullets for my muzzle loader.

Bigslug

11-21-2022, 10:02 AM

I think Charlie b is pointing in a good direction with his mention of nose-pour molds: getting the perfect sprue cut is a challenging thing. I've definitely proven to myself that protruding spurs under the gas check are detrimental to accuracy, and if pits torn out by the cutting action cause problems as well, moving that entire process to the nose would have much to recommend it.

Larry Gibson

11-21-2022, 03:14 PM

When I inspect my match cast bullets, if they pass a visual test under a magnifying glass and have an uneven sprue cut, I lay the bullet on a block of lead and cut the uneven sprue off with a sharp knife. The bullet is then weighed for sorting. With such bullets the Hornady GCs fit evenly and the shnk bottoms out evenly in the GC using the GC seater on my 450 Lyman with a .311 H&I die which initially crimps the GC.

charlie b

11-21-2022, 11:39 PM

Well, a bit of a setback today. Loaded up some more. The 38gn load of 4166 and then three of n150, 38, 39 and 40gn. The max load for n150 and 208gn bullets is just over 40gn at just under 2400fps. Should be about right.

Set everything up at the 600yd target line this morning. Temps were in the mid 40's and small gusts, less than 5mph. Lots of mirage.

I started out and couldn't hit anything. Then realized I had the scope set for 500yd. Changed that and tried again. Then remembered the last windage was for a 5mph wind and it was near calm today, so more adjusting. Finally got a few close to the gong. The mirage was making things a little difficult as well.

The funny stuff started with the 39 and 40gn loads. 3 rounds into a smaller area, then one off the board. 3 more ok, then two off. All of this tracked with some large jumps in vel. Then I realized it was really easy to chamber some of the rounds. Another duh moment. One of my more brilliant ideas was that my crimp die might be damaging the bullets so I backed it off a little. I think too much. I was probably just pushing the bullets deeper in the case, resulting in wild velocity swings.

And just to add to the problems, the mirage made the video not as informative. No 'trails' to follow, just impact points.

Back to the drawing board. :(

Good news is, the bullets that did show 'correct' velocities tracked pretty true to the target at 600yd. So, I have a couple of loads that will work at this range.

Forrest r

11-22-2022, 04:41 AM

A couple years ago I was testing the xcb in a 308w. Kept getting groups like these.
https://i.imgur.com/JFXg89A.jpg

Didn't matter what powder I used/tested I kept getting fliers and when I ran them faster I got shotgun patterns instead of groups (+/- 12" groups for 10-shots @ 100yds).

When I cast my bullets I always run the sprue plate back and forth over the bullet bases several times. Doing this gets the bases flat and shows any imperfections.

I make my own gc's out of aluminum and tried flat cup bottoms along with a beveled edged bottom pictured below.
https://i.imgur.com/LPn6FPn.jpg

I made special dies for the lyman 450 and a swaging press to nose form bullets along with seating the gc's.

I've ran into nose slump issues pictured below with using bullets cast from a 2-cavity crmer mold. 1 cavity is a sp bullet the other a hp/flat nosed bullet.
https://i.imgur.com/uLdIPcZ.jpg

Ran into lube issues with the lee 312-160tl bullet blowing out at 2600fps.
https://i.imgur.com/y5CttId.jpg?1
Added more lube and the 2600fps group tightened up.
https://i.imgur.com/x4M2uh5.jpg?1

I can drive the lee tl bullet pretty fast with reasonable accuracy. But every time I tried to push the xcb bullet it was a disaster. Same alloy, same gc's, same dies, rifle, etc. I can use the lee bullet with 37gr of h335 and get 2600fps+ 10-shot groups @ 100yds that are 2" or less. 37gr with the xcb and it was hard to keep 10-shot on paper @ 100yds.

Finely decided to order 1000 hornady gc's and seat 20 of them on the cast xcb bullets. I loaded those 20 bullets up with that 37gr load of H335 and went to the range & set a target up @ 100yds. I shot 2 different 10-shot groups and I couldn't believe it. I still had fliers with 7/8 bullets touching. The fliers made the groups +/- 1 1/4". Of all the times not to take a picture, darn wasn't thinking. Actually I was ecstatic with what I saw.

The only thing I can think is that my al gc's were too hard and weren't staying on the xcb bullet with the higher pressured loads.

Larry Gibson

11-22-2022, 08:53 AM

Forrest r

I never got any consistent accuracy with aluminum GCs [my own make using .014 flashing] over 2000 - 2200 fps with any bullet. Best success up through 2200 fps was in the 14' twist. N ever tried in the 16" twist. My own brass GCs (.014) do well up through 2600 fps in the 14" twist. Again, never tried them in my 16" twist. Have been using Hornady GCs mostly for HV.

At HV/RRPM the loss of the GC can definately have a detrimental effect on accuracy.

charlie b

11-22-2022, 09:45 AM

I had horrible trouble with fliers until I tightened up the weight sorting. I started out using batches of bullets in 0.5gn groups (eg, 165.5 to 165.9). That helped a bit, but, I did not get to 1 1/2 MOA without going to 0.1gn batches.

I also found same as Larry has mentioned. Selecting only those at the high end of the weight spread also helps. For example, I usually have a spread of about 1.0gn when I cast, eg, 210.6gn to 211.6gn. The 211.6gn bullets give a bit better groups than the 210.6gn batch. This is even more noticeable as the speeds increase.

I will only use Hornady checks, simply because of how deep I have to seat the bullets in my .308. If the GC is not a crimp type I don't trust it when seated below the case neck.

charlie b

12-18-2022, 04:25 PM

Well, pushed the limit a bit again. I tried the n150 and the accuracy was not there at all, even with loads in the 2200fps range. But, I found some H4350 for sale so I got some. This is a lot slower than the previous 4166 so I was hoping it would help a little.

For reference the Sierra max load for a 200gn SMK is 45.1gn and 2450fps. I loaded up my 'reference' load of 31.0gn of 4166 and then 43, 44 and 45gn of H4350. Bullets were all 211.6 or 211.5gn. Bad news is the video camera battery went dead. The good news is I still track where the shots hit so I have a decent idea (within limits) of how well they shoot.

Surprise, the 45gn load average was 2425fps with an es of 33fps and yielded almost as good a 'group' as the 31gn reference (1970fps). Temp was in the low 40's.

Also, unlike the max 4166 loads, the cases were not sticky at all to extract.

So, Larry's idea about a 'softer' push from the slower powders has shown some better results. This is as fast as I will drive these bullets given all the book data out there.

So, will load up some more and see how they do at 600yd. Also will punch some paper with it next time. Will have to wait a while as other things come up.

charlie b

03-20-2023, 09:33 PM

So, have done a lot of shooting since last post.

The heavy 4350 loads and 4166 loads did not show consistent performance. One week I could keep everything on a piece of paper at 500yd (including 5 round 4 and 5.5 inch groups), other days I was lucky to hit it (8.5x11 targets). I have compared loads with bullets at the top of the weight curve and they sometimes do better, but, not always. Also tracked wind and temperature and they do not seem to matter. The only thing I can come up with is that I am on the edge of rotational stability.

I still get decent groups at 500yd if I keep the vel around 2000fps so that is what I will do for now.

So, I am back to the lower velocities I started at.

I am still considering a slower twist barrel so my quest is not over :)

4575wcf

04-06-2023, 09:41 PM

I have been shooting cast bullets for quite awhile in the lever action/military cast bullet matches. Bullet performance on game didn't matter, I had unmentionable bullets for that. I always cast with Hornady hard lead shot and quenched from the mold into cold water. I had good accuracy with my bullets on the 200 yard ram, and enough stomp to knock him down as long as I used the heaviest bullets I could get for the caliber. Then the shortages hit and I was not long building up a hunting rifle for cast. I chose the 8 x 54KJ round because it fits the small ring '91 Mauser I had so very well. It is a necked up 6.5 x 55 Swede and it has killed literally thousands of Scandinavian moose in the Norwegian Krag Jorgensen and the Swedish Mauser. Not that the 6.5 x 55 won't put them down, but the 8 x 54 puts them down a bit better, and so it exists. Now it has gone obsolete more or less, Scandinavian shooters are no different than any one else when new and better products become available.
So with the rifle built up on the '91 with a '93 Turkish 8 x 57 barrel shortened up from the breech end to clean up the chamber and a modified 6.5 x 55 Lee die set, we are off and running. The rifle shoots the Saeco 8 mm 190 RN cast in my regular alloy into an inch at 50 yards all day long up to about exactly 1700fps. The it just quits shooting. Period. I exhumed a few bullets from the soft dirt bank on the property and really there isn't anything noticeably wrong with them at a higher velocity. The target tells a different story with obvious oblong holes. I think I have been confronted with the maximum rpm that this cast bullet alloy will withstand without the rifling grip breaking loose. I am already casting them a bit hard for hunting IMO. With my Mauser 1-9.45 twist that threshold should and does seem to happen at almost exactly 1700 fps. One manufacturer makes an 8mm barrel with .324 grooves and 1-12 twist; I think that will be the blank going into the rifle next since it is almost affordable, but a heck of a lot of work. Again. So many folks that have fired so many more cast bullets than I seem to be arriving at the same conclusion I don't think I need to reinvent the wheel.